BACKGROUND
the successful colonisation of temperate biomes by tropical lineages has involved the crossing of a significant physiological barrier that has acted as an important filter  <cit> .
as a consequence, approximately half of all plant families remain restricted to the tropics  <cit> .
lineages that have made the transition to temperate biomes have experienced different fates with some lineages expanding their ranges to occupy highly disjunct areas where a suitable climate occurs, with distributions spanning both different continents and different hemispheres.
whilst the processes responsible for such patterns are complex , long-distance dispersal  events have been proposed for many such disjunctions and they may have acted as triggers for diversification  <cit> .
thorne  <cit>  recognised fifteen temperate disjunction patterns, several of which have since been the focus of molecular phylogenetic studies to understand the extent to which vicariance and dispersal explain biogeographic patterns in temperate plant lineages .
one of the patterns documented by thorne  <cit>  was the ‘north–south temperate disjunction’ which describes groups that are widespread in the northern temperate region and that also occur in one or more of the southern temperate zones .
the convolvuleae  choisy is one of  <dig> tribes within the predominantly tropical plant family convolvulaceae juss.
<cit> .
it is one of only two tribes within the family to have widely colonised temperate regions  and it exhibits thorne’s ‘north–south temperate disjunction’ pattern.
the convolvuleae comprises three genera namely convolvulus l., calystegia r.br.
and polymeria r.br.. convolvulus is the largest, comprising  <dig> species  <cit> .
it has a main centre of diversity in the mediterranean and western asia, with further centres of diversity in eastern asia and in temperate south america, southern and eastern africa and australasia; i.e., the three temperate zones of the southern hemisphere.
species also occur in north america, although they are few in number.
calystegia is readily distinguished from convolvulus based on morphological characters  but molecular analyses suggest it is nested within the larger convolvulus clade  <cit> .
calystegia is taxonomically complex  <cit>  with c.  <dig> species and more than  <dig> distinct taxa currently accepted  <cit> .
the centre of diversity for calystegia is in california where nearly half of the described taxa occur  <cit> .
other centres of diversity for calystegia are found in eastern asia and, to a lesser extent europe and the mediterranean.
calystegia also occurs in temperate regions of the southern hemisphere.
finally, the australasian endemic polymeria is the smallest of the three genera of convolvuleae with eight species recognised  <cit> .
molecular analyses place it as sister group to the remainder of convolvuleae  <cit> .
a recent study by williams et al.
<cit>  established a robust phylogenetic hypothesis of the convolvuleae that sampled 62 % of species diversity in the tribe and was based on data from both the nuclear its region and the chloroplast matk and rbcl regions.
the goal of this paper is to utilise that phylogenetic framework to determine how the north–south temperate disjunction pattern displayed by convolvuleae was generated.
specifically, we aim to  determine the number, timing and cause  of amphitropical and transoceanic disjunctions in the pan-temperate convolvuleae and  determine how major disjunctions in the history of the group may have impacted on diversification rates.
RESULTS
convolvulaceae–solanaceae analysis
an alignment comprising  <dig> species of convolvulaceae  and  <dig> species of solanaceae  and  <dig> characters from the matk and rbcl regions  was used to establish divergence times within convolvulaceae.
the rbcl region was coded with missing data for  <dig> taxa, of which four were convolvuleae.
a chronogram with major groups is summarised in additional file  <dig>  the convolvulaceae are resolved to have arisen  <dig>   ma, in agreement with särkinen et al.
<cit> .
age estimates established for nodes within solanaceae are also in agreement with särkinen et al.
<cit> .
within convolvulaceae, the convolvuloideae sensu stefanović et al.
<cit>  is resolved as  <dig>   myr old, with the convolvuleae crown group  resolved at  <dig>   ma.
convolvuleae analysis
five areas of endemism within convolvuleae were delimited using upgma clustering of species by country distribution data .
a convolvuleae alignment consisted of  <dig> species of convolvuleae  and  <dig> characters from the rbcl, matk and its regions .
divergence times estimated in beast using calibration points derived from the solanaceae-convolvulaceae analysis above and ancestral area reconstructions estimated using lagrange are provided in fig.
1b with table  <dig> summarising the information for key nodes of interest.fig.
<dig> phylogeny of convolvuleae.
a) map depicting the areas of endemism for convolvuleae delimited using upgma analysis.
b) dated phylogeny of convolvuleae inferred in beast from analysis of the concatenated its, matk and rbcl dataset.
node bars represent 95 % hpd estimates.
scale bar represent millions of years before present.
coloured branches and taxon names indicate the distribution area inferred in lagrange, as shown in fig.
1a.
black branches indicate ambiguous areas .
grey branches indicate a multiple area distribution.
numbers at the top-left of nodes are referred to in table  <dig>  * indicate the location of calibrated nodes.
black circles on nodes indicate nodes with bayesian posterior probabilities of at least  <dig>
lagrange optimisations and beast minimum age estimates for key nodes in the convolvuleae analysis.
node numbers are labelled in fig.
1b.
lagrange splits refer to areas shown in fig.
1a in the format x/y where x relates to the top branch, and y relates to the bottom branch exiting the labelled node.
log likelihoods  and relative probabilities  are given for each lagrange optimisation within two lnl of the most likely split optimisation.
bayesian posterior probabilities , mean node ages and 95 % highest posterior density  estimates inferred in beast are given for each node
the ancestral area of the convolvulus + calystegia clade is inferred to be the mediterranean-and-middle-east .
dispersal between contiguous areas ) occurred frequently .
movement between disjunct  areas has been much less common and eight such events are inferred.
these are, in order of recency:  amphitropical disjunction between australasia  and the mediterranean-and-middle-east   = 1) dated  <dig>  ma :  <dig> – <dig>  ma) ,  northern hemisphere disjunction between the mediterranean-and-middle-east  and north america   dated  <dig>  ma  ,  northern hemisphere disjunction between central-and-north-eastern-asia  and north america  , dated  <dig>  ma  ,  amphitropical disjunction between the mediterranean-and-middle-east  and southern-and-eastern-africa   dated  <dig>  ma  ,  transoceanic southern hemisphere disjunction between southern-and-eastern-africa  and australasia  , dated  <dig>  ma  ,  weakly supported transoceanic southern hemisphere disjunction between southern-and-eastern-africa  and south america   dated as  <dig>  ma  ,  weakly supported  amphitropical disjunction between south america  and north america , dated  <dig>  ma   and  weakly supported  amphitropical disjunction between north america  and the southern hemisphere , south america  or both, node 15), dated  <dig>  ma
diversification rate analysis
bamm analysis found support for rate shifts within the convolvuleae phylogeny compared with a single rate model  >  <dig> for 2– <dig> shifts).
the maximum a posteriori  probability rate shift configuration, which alone explains 56 % of the data, infers two rate shifts: one on the stem branch of the southern hemisphere clade  and one on the stem branch of calystegia  .
mean speciation rates  within the circum-south temperate  clade  and calystegia  are over twice those of the tribe as a whole .
extinction rates  however are also slightly higher in both the cst clade  and calystegia  than in convolvuleae as a whole .
mean diversification rates  in the cst clade  are therefore nearly three times greater than in the tree as a whole , while those in calystegia are over twice as fast  as convolvuleae in general.
extinction rates are inferred to have remained fairly constant over the history of the tribe, however speciation rates appear to have increased considerably in the last  <dig>  myr .fig.
<dig> the maximum a posteriori probability rate shift configuration inferred by bamm.
the maximum a posteriori probability rate shift configuration inferred by bamm analysis of the convolvuleae concatenated its, matk and rbcl dataset.
branches are coloured according to the rate inferred along that branch.
speciation rates are given as species myr− <dig>  two rate shifts are inferred: a) the stem branch of the circum-south temperate clade ; b) the stem branch of calystegia
discussion
both the world’s oceans and the equatorial tropics present barriers to dispersal of temperate lineages, potentially limiting exchange between the disjunct temperate zones of the world.
in convolvuleae, we observe four amphitropical and four transoceanic disjunctions in the history of the group with an increase in diversification rate associated with one amphitropical disjunction .
a second increase in diversification rate is observed in calystegia which also exhibits a transoceanic disjunction.
the four amphitropical disjunctions are spread throughout the history of the tribe .
the earliest dates to the mid-miocene  ma; node 1; fig.
1b; table 1) and separates the australasian endemic polymeria from the remainder of convolvuleae , for which the mediterranean-and-middle-east is resolved as the ancestral distribution area.
this spatio-temporal pattern is consistent with the inferred timing of the disjunction between australia and eurasia in carex subsect.
spirostachyae  and in halosarcia .
escudero et al.
<cit>  invoked ldd to explain this disjunction although the timing is coincident with the mid-miocene climatic optimum 15–17 ma, which saw the expansion of tropical forests, an event that is thought to have facilitated the dispersal of tropical plant and animal groups between africa and asia  <cit> .
it is plausible that a corresponding contraction of temperate areas may have led to the disjunction apparent in these groups.
särkinen et al.
<cit>  resolved a similar sister group relationship in solanum between the western mediterranean–macaronesian endemic normania clade and the australasian endemic archaesolanum clade and an australian–northern hemisphere disjunction was also inferred for atriplex  <cit> .
however, the timing of these was more recent  suggesting that the history of australasian–northern hemisphere disjunctions is complex with multiple, temporally distinct events likely involved.
a second amphitropical disjunction in convolvuleae is the result of the colonisation of the southern hemisphere by convolvulus during the late miocene to pliocene c.  <dig>   ma .
the most probable scenario involves dispersal from the mediterranean-and-middle-east into southern-and-eastern-africa, followed by dispersal from there to australasia c.  <dig>   ma  and south america c.  <dig>   ma  although the precise relationships of african and american taxa are not well supported.
the mountains of the east african rift system, which link southern africa with the horn of africa are thought to have originated c. 12–40 ma  <cit>  and they provide a plausible trans-african dispersal corridor for convolvuleae as has been suggested for other temperate taxa .
it is notable that whilst some african amphitropical disjunctions are inferred to be pre-pliocene  ma  <cit> ; hyacinthoideae,  <dig>   ma  <cit> ; thamnosma,  <dig>   ma  <cit> ), plio– pleistocene disjunctions, consistent with that observed in convolvuleae have been reported in a number of groups.
for example, colonisation of southern africa from the north through this corridor has been inferred in apium  ma  <cit> ), ranunculus  ma  <cit> ) and scabiosa  ma  <cit> ) whilst south to north colonisation has been inferred for androcymbium  ma and  <dig>   ma  <cit> ) and, very recently in senecio  ma  <cit> ).
the remaining amphitropical disjunctions are observed in the new world.
pleistocene dispersal  ma) from south america to north america is inferred in the cst group .
a southwards dispersal in calystegia  is inferred to have occurred at a similar time c.  <dig>   ma resulting in the colonisation of south america and australasia.
however, limited support  or taxonomic uncertainty  means that these patterns should be interpreted with caution and the evolution and biogeography of the calystegia clade in particular would benefit from further research.
these limitations notwithstanding, amphitropical american disjunctions of recent origin have been inferred in a range of groups with evidence for dispersal in both directions  <cit> .
bird mediated dispersal has frequently been proposed as responsible for such disjunctions due to the seasonal migration of birds between the northern and southern hemispheres .
whilst evidence for this is largely anecdotal, epizoochoric bird-mediated ldd between california and chile has been demonstrated in lepidium  <cit> .
in the case of convolvulus, viable seeds of convolvulus arvensis have been recovered from the digestive tract of migratory killdeer  up to six days after ingestion  <cit> .
importantly however, long-distance internal transport of seeds, even in generally larger waterbirds has been shown to be limited to around 300 km making extreme long-distance endozoochoric dispersal unlikely  <cit> .
montane south american species of convolvulus such as c. crenatifolius and c. montanus are frequently found above  <dig> m  <cit>  and the andean high mountains, which are of late miocene origin  <cit> , may have provided a suitable route for the dispersal of temperate convolvuleae lineages across the neotropics.
remarkably few transoceanic dispersal events are necessary to explain the global distribution of the convolvuleae, in contrast to groups such as fabaeae  <cit> .
between the major southern hemisphere landmasses, we infer only two such dispersal events which both occurred  <dig> – <dig>  ma, long after the breakup of the gondwanan landmass and too recent to involve an antarctic corridor  <cit> .
divergence time estimates for southern temperate plant groups indicate a wide range of ages, with convolvuleae disjunctions among the most recent  <cit> .
whilst detailed information on dispersal mechanisms within the tribe are lacking, the variability of seed characteristics in convolvulaceae  <cit>  and evidence of long-distance oceanic seed dispersal elsewhere in the family  <cit>  anecdotally support an oceanic dispersal hypothesis for the southern hemisphere distribution of convolvuleae.
two independent events in the late miocene/pliocene are inferred to be responsible for the earliest colonisation of north america.
the most likely scenario for the calystegia clade is dispersal from the mediterranean-and-middle-east into eastern asia c.  <dig>  ma  and from there into north america c.  <dig>   ma .
the east asian–north american disjunction is one of the best studied disjunctions with numerous examples of movement between the two regions throughout the cenozoic  <cit> .
the continents of the northern hemisphere were connected until  <dig> – <dig>  ma when the bering land bridge joining north america and eastern asia was finally severed  <cit> .
a circum-arctic floral region spanning this landmass prior to the severing of the land connections is frequently hypothesised as responsible for both the similarity and diversity of the flora in these regions .
given our estimated age for the northern hemisphere disjunction in convolvuleae we are unable to reject a vicariance hypothesis for the origin of calystegia in north america, in contrast to all other disjunctions we have inferred.
in the case of convolvulus simulans , dispersal directly from the mediterranean-and-middle-east to north america c.  <dig>   ma is inferred.
a disjunction between the mediterranean regions of north america and europe  is well documented  and long distance dispersal to north america from the mediterranean during the late miocene/pliocene has been inferred in a number of lineages .
with regards widespread and naturalised convolvulus that were excluded from our analyses, comparison between the phylogeny estimated in williams et al.
<cit>  and our biogeographic inference suggests that both excluded species  probably originated in the mediterranean-and-middle-east region.
the diversification rate analysis reveals mean diversification rates for convolvuleae of  <dig>  species myr− <dig>  above the estimated diversification rates of angiosperms as a whole  leading to mean diversification rates  which exceed those of adaptive radiations such as the hawaiian radiation of bidens   <cit> .
bamm suggests the elevated diversification rates are linked to an increase in speciation rate as opposed to a decrease in extinction rate .
the southern hemisphere clade contains at least two long-distance oceanic dispersal events within the southern hemisphere  and at least two amphitropical dispersal events , with the shift to elevated diversification rates associated with the initial dispersal into the southern hemisphere in the late miocene or pliocene.
this is consistent with other studies demonstrating the impact of miocene dispersal events important in promoting diversification  <cit> .table  <dig> convolvuleae diversification rates
estimated mean 90 % hpd  speciation , extinction  and net diversification rates inferred in bamm for convolvuleae, and two clades with shifts to increased diversification rates .
rates are given in species myr−1
the second diversification rate shift is observed in calystegia.
bamm finds support, albeit less strongly, for a shift to increased diversification rates on the stem branch of calystegia , leading to mean diversification rates , over twice as high as those found in convolvuleae as a whole.
most of the diversity of calystegia is in north america and specifically california  <cit>  and dispersal from east asia into north america, again in the miocene/pliocene could also have been an important trigger for diversification within the group.
CONCLUSIONS
in summary, our results indicate that the convolvuleae has successfully colonised every continent of the world with a temperate biome in c.  <dig> myr.
the tropics and major oceans have been significant dispersal barriers for the group with only eight major disjunctions underlying this broad ‘north–south temperate’ distribution pattern.
in keeping with many other disjunct temperate lineages, long-distance dispersal is inferred as the main process explaining the patterns observed although for one american-eurasian disjunction we cannot exclude vicariance resulting from the severing of the bering land bridge.
even though dispersal is the primary process generating the patterns observed, spatio-temperal congruence is observed with other temperate disjunct groups suggesting a common explanation for the patterns observed.
the convolvuleae exhibits high diversification rates overall when compared to other angiosperm groups and the colonisation of the temperate zones of the three southern continents within the last c.  <dig> myr is associated with an increase in diversification rate with lineage accumulation rates in the clade comparable to those reported for adaptive radiations.
the calystegia clade also exhibits a high diversification rate which probably reflects rapid diversification following colonisation of western north america.
the convolvuleae thus provide a striking example of the ability of temperate lineages to rapidly colonise highly disjunct areas worldwide and to diversify.

 the successful colonisation of temperate biomes by tropical lineages has involved the crossing of a significant physiological barrier that has acted as an important filter. as a consequence, approximately half of all plant families remain restricted to the tropics. lineages that have made the transition to temperate biomes have experienced different fates with some lineages expanding their ranges to occupy highly disjunct areas where a suitable climate occurs, with distributions spanning both different continents and different hemispheres. whilst the processes responsible for such patterns are complex, long-distance dispersal events have been proposed for many such disjunctions and they may have acted as triggers for diversification. thorne recognised fifteen temperate disjunction patterns, several of which have since been the focus of molecular phylogenetic studies to understand the extent to which vicariance and dispersal explain biogeographic patterns in temperate plant lineages. one of the patterns documented by thorne was the ‘north–south temperate disjunction’ which describes groups that are widespread in the northern temperate region and that also occur in one or more of the southern temperate zones. the convolvuleae choisy is one of tribes within the predominantly tropical plant family convolvulaceae juss.. it is one of only two tribes within the family to have widely colonised temperate regions and it exhibits thorne’s ‘north–south temperate disjunction’ pattern. the convolvuleae comprises three genera namely convolvulus l., calystegia r.br. and polymeria r.br.. convolvulus is the largest, comprising species. it has a main centre of diversity in the mediterranean and western asia, with further centres of diversity in eastern asia and in temperate south america, southern and eastern africa and australasia; i.e., the three temperate zones of the southern hemisphere. species also occur in north america, although they are few in number. calystegia is readily distinguished from convolvulus based on morphological characters but molecular analyses suggest it is nested within the larger convolvulus clade. calystegia is taxonomically complex with c. species and more than distinct taxa currently accepted. the centre of diversity for calystegia is in california where nearly half of the described taxa occur. other centres of diversity for calystegia are found in eastern asia and, to a lesser extent europe and the mediterranean. calystegia also occurs in temperate regions of the southern hemisphere. finally, the australasian endemic polymeria is the smallest of the three genera of convolvuleae with eight species recognised. molecular analyses place it as sister group to the remainder of convolvuleae. a recent study by williams et al. established a robust phylogenetic hypothesis of the convolvuleae that sampled 62 % of species diversity in the tribe and was based on data from both the nuclear its region and the chloroplast matk and rbcl regions. the goal of this paper is to utilise that phylogenetic framework to determine how the north–south temperate disjunction pattern displayed by convolvuleae was generated. specifically, we aim to determine the number, timing and cause of amphitropical and transoceanic disjunctions in the pan-temperate convolvuleae and determine how major disjunctions in the history of the group may have impacted on diversification rates.  convolvulaceae–solanaceae analysis an alignment comprising species of convolvulaceae and species of solanaceae and characters from the matk and rbcl regions was used to establish divergence times within convolvulaceae. the rbcl region was coded with missing data for taxa, of which four were convolvuleae. a chronogram with major groups is summarised in additional file the convolvulaceae are resolved to have arisen ma, in agreement with särkinen et al.. age estimates established for nodes within solanaceae are also in agreement with särkinen et al.. within convolvulaceae, the convolvuloideae sensu stefanović et al. is resolved as myr old, with the convolvuleae crown group resolved at ma. convolvuleae analysis five areas of endemism within convolvuleae were delimited using upgma clustering of species by country distribution data. a convolvuleae alignment consisted of species of convolvuleae and characters from the rbcl, matk and its regions. divergence times estimated in beast using calibration points derived from the solanaceae-convolvulaceae analysis above and ancestral area reconstructions estimated using lagrange are provided in fig. 1b with table  summarising the information for key nodes of interest.fig. phylogeny of convolvuleae. a) map depicting the areas of endemism for convolvuleae delimited using upgma analysis. b) dated phylogeny of convolvuleae inferred in beast from analysis of the concatenated its, matk and rbcl dataset. node bars represent 95 % hpd estimates. scale bar represent millions of years before present. coloured branches and taxon names indicate the distribution area inferred in lagrange, as shown in fig. 1a. black branches indicate ambiguous areas. grey branches indicate a multiple area distribution. numbers at the top-left of nodes are referred to in table  * indicate the location of calibrated nodes. black circles on nodes indicate nodes with bayesian posterior probabilities of at least lagrange optimisations and beast minimum age estimates for key nodes in the convolvuleae analysis. node numbers are labelled in fig. 1b. lagrange splits refer to areas shown in fig. 1a in the format x/y where x relates to the top branch, and y relates to the bottom branch exiting the labelled node. log likelihoods and relative probabilities are given for each lagrange optimisation within two lnl of the most likely split optimisation. bayesian posterior probabilities, mean node ages and 95 % highest posterior density estimates inferred in beast are given for each node the ancestral area of the convolvulus + calystegia clade is inferred to be the mediterranean-and-middle-east. dispersal between contiguous areas ) occurred frequently. movement between disjunct areas has been much less common and eight such events are inferred. these are, in order of recency: amphitropical disjunction between australasia and the mediterranean-and-middle-east  = 1) dated  ma: –  ma), northern hemisphere disjunction between the mediterranean-and-middle-east and north america dated  ma, northern hemisphere disjunction between central-and-north-eastern-asia and north america, dated  ma, amphitropical disjunction between the mediterranean-and-middle-east and southern-and-eastern-africa dated  ma, transoceanic southern hemisphere disjunction between southern-and-eastern-africa and australasia, dated  ma, weakly supported transoceanic southern hemisphere disjunction between southern-and-eastern-africa and south america dated as  ma, weakly supported amphitropical disjunction between south america and north america, dated  ma and weakly supported amphitropical disjunction between north america and the southern hemisphere, south america or both, node 15), dated  ma diversification rate analysis bamm analysis found support for rate shifts within the convolvuleae phylogeny compared with a single rate model  >  for 2– shifts). the maximum a posteriori probability rate shift configuration, which alone explains 56 % of the data, infers two rate shifts: one on the stem branch of the southern hemisphere clade and one on the stem branch of calystegia. mean speciation rates within the circum-south temperate clade and calystegia are over twice those of the tribe as a whole. extinction rates however are also slightly higher in both the cst clade and calystegia than in convolvuleae as a whole. mean diversification rates in the cst clade are therefore nearly three times greater than in the tree as a whole, while those in calystegia are over twice as fast as convolvuleae in general. extinction rates are inferred to have remained fairly constant over the history of the tribe, however speciation rates appear to have increased considerably in the last myr.fig. the maximum a posteriori probability rate shift configuration inferred by bamm. the maximum a posteriori probability rate shift configuration inferred by bamm analysis of the convolvuleae concatenated its, matk and rbcl dataset. branches are coloured according to the rate inferred along that branch. speciation rates are given as species myr− two rate shifts are inferred: a) the stem branch of the circum-south temperate clade; b) the stem branch of calystegia discussion both the world’s oceans and the equatorial tropics present barriers to dispersal of temperate lineages, potentially limiting exchange between the disjunct temperate zones of the world. in convolvuleae, we observe four amphitropical and four transoceanic disjunctions in the history of the group with an increase in diversification rate associated with one amphitropical disjunction. a second increase in diversification rate is observed in calystegia which also exhibits a transoceanic disjunction. the four amphitropical disjunctions are spread throughout the history of the tribe. the earliest dates to the mid-miocene ma; node 1; fig. 1b; table 1) and separates the australasian endemic polymeria from the remainder of convolvuleae, for which the mediterranean-and-middle-east is resolved as the ancestral distribution area. this spatio-temporal pattern is consistent with the inferred timing of the disjunction between australia and eurasia in carex subsect. spirostachyae and in halosarcia. escudero et al. invoked ldd to explain this disjunction although the timing is coincident with the mid-miocene climatic optimum 15–17 ma, which saw the expansion of tropical forests, an event that is thought to have facilitated the dispersal of tropical plant and animal groups between africa and asia. it is plausible that a corresponding contraction of temperate areas may have led to the disjunction apparent in these groups. särkinen et al. resolved a similar sister group relationship in solanum between the western mediterranean–macaronesian endemic normania clade and the australasian endemic archaesolanum clade and an australian–northern hemisphere disjunction was also inferred for atriplex. however, the timing of these was more recent suggesting that the history of australasian–northern hemisphere disjunctions is complex with multiple, temporally distinct events likely involved. a second amphitropical disjunction in convolvuleae is the result of the colonisation of the southern hemisphere by convolvulus during the late miocene to pliocene c. ma. the most probable scenario involves dispersal from the mediterranean-and-middle-east into southern-and-eastern-africa, followed by dispersal from there to australasia c. ma and south america c. ma although the precise relationships of african and american taxa are not well supported. the mountains of the east african rift system, which link southern africa with the horn of africa are thought to have originated c. 12–40 ma and they provide a plausible trans-african dispersal corridor for convolvuleae as has been suggested for other temperate taxa. it is notable that whilst some african amphitropical disjunctions are inferred to be pre-pliocene ma; hyacinthoideae, ma; thamnosma, ma ), plio– pleistocene disjunctions, consistent with that observed in convolvuleae have been reported in a number of groups. for example, colonisation of southern africa from the north through this corridor has been inferred in apium ma ), ranunculus ma ) and scabiosa ma ) whilst south to north colonisation has been inferred for androcymbium ma and ma ) and, very recently in senecio ma ). the remaining amphitropical disjunctions are observed in the new world. pleistocene dispersal ma) from south america to north america is inferred in the cst group. a southwards dispersal in calystegia is inferred to have occurred at a similar time c. ma resulting in the colonisation of south america and australasia. however, limited support or taxonomic uncertainty means that these patterns should be interpreted with caution and the evolution and biogeography of the calystegia clade in particular would benefit from further research. these limitations notwithstanding, amphitropical american disjunctions of recent origin have been inferred in a range of groups with evidence for dispersal in both directions. bird mediated dispersal has frequently been proposed as responsible for such disjunctions due to the seasonal migration of birds between the northern and southern hemispheres. whilst evidence for this is largely anecdotal, epizoochoric bird-mediated ldd between california and chile has been demonstrated in lepidium. in the case of convolvulus, viable seeds of convolvulus arvensis have been recovered from the digestive tract of migratory killdeer up to six days after ingestion. importantly however, long-distance internal transport of seeds, even in generally larger waterbirds has been shown to be limited to around 300 km making extreme long-distance endozoochoric dispersal unlikely. montane south american species of convolvulus such as c. crenatifolius and c. montanus are frequently found above m and the andean high mountains, which are of late miocene origin, may have provided a suitable route for the dispersal of temperate convolvuleae lineages across the neotropics. remarkably few transoceanic dispersal events are necessary to explain the global distribution of the convolvuleae, in contrast to groups such as fabaeae. between the major southern hemisphere landmasses, we infer only two such dispersal events which both occurred –  ma, long after the breakup of the gondwanan landmass and too recent to involve an antarctic corridor. divergence time estimates for southern temperate plant groups indicate a wide range of ages, with convolvuleae disjunctions among the most recent. whilst detailed information on dispersal mechanisms within the tribe are lacking, the variability of seed characteristics in convolvulaceae and evidence of long-distance oceanic seed dispersal elsewhere in the family anecdotally support an oceanic dispersal hypothesis for the southern hemisphere distribution of convolvuleae. two independent events in the late miocene/pliocene are inferred to be responsible for the earliest colonisation of north america. the most likely scenario for the calystegia clade is dispersal from the mediterranean-and-middle-east into eastern asia c.  ma and from there into north america c. ma. the east asian–north american disjunction is one of the best studied disjunctions with numerous examples of movement between the two regions throughout the cenozoic. the continents of the northern hemisphere were connected until –  ma when the bering land bridge joining north america and eastern asia was finally severed. a circum-arctic floral region spanning this landmass prior to the severing of the land connections is frequently hypothesised as responsible for both the similarity and diversity of the flora in these regions. given our estimated age for the northern hemisphere disjunction in convolvuleae we are unable to reject a vicariance hypothesis for the origin of calystegia in north america, in contrast to all other disjunctions we have inferred. in the case of convolvulus simulans, dispersal directly from the mediterranean-and-middle-east to north america c. ma is inferred. a disjunction between the mediterranean regions of north america and europe is well documented and long distance dispersal to north america from the mediterranean during the late miocene/pliocene has been inferred in a number of lineages. with regards widespread and naturalised convolvulus that were excluded from our analyses, comparison between the phylogeny estimated in williams et al. and our biogeographic inference suggests that both excluded species probably originated in the mediterranean-and-middle-east region. the diversification rate analysis reveals mean diversification rates for convolvuleae of species myr− above the estimated diversification rates of angiosperms as a whole leading to mean diversification rates which exceed those of adaptive radiations such as the hawaiian radiation of bidens. bamm suggests the elevated diversification rates are linked to an increase in speciation rate as opposed to a decrease in extinction rate. the southern hemisphere clade contains at least two long-distance oceanic dispersal events within the southern hemisphere and at least two amphitropical dispersal events, with the shift to elevated diversification rates associated with the initial dispersal into the southern hemisphere in the late miocene or pliocene. this is consistent with other studies demonstrating the impact of miocene dispersal events important in promoting diversification.table convolvuleae diversification rates estimated mean 90 % hpd speciation, extinction and net diversification rates inferred in bamm for convolvuleae, and two clades with shifts to increased diversification rates. rates are given in species myr−1 the second diversification rate shift is observed in calystegia. bamm finds support, albeit less strongly, for a shift to increased diversification rates on the stem branch of calystegia, leading to mean diversification rates, over twice as high as those found in convolvuleae as a whole. most of the diversity of calystegia is in north america and specifically california and dispersal from east asia into north america, again in the miocene/pliocene could also have been an important trigger for diversification within the group.  in summary, our results indicate that the convolvuleae has successfully colonised every continent of the world with a temperate biome in c. myr. the tropics and major oceans have been significant dispersal barriers for the group with only eight major disjunctions underlying this broad ‘north–south temperate’ distribution pattern. in keeping with many other disjunct temperate lineages, long-distance dispersal is inferred as the main process explaining the patterns observed although for one american-eurasian disjunction we cannot exclude vicariance resulting from the severing of the bering land bridge. even though dispersal is the primary process generating the patterns observed, spatio-temperal congruence is observed with other temperate disjunct groups suggesting a common explanation for the patterns observed. the convolvuleae exhibits high diversification rates overall when compared to other angiosperm groups and the colonisation of the temperate zones of the three southern continents within the last c. myr is associated with an increase in diversification rate with lineage accumulation rates in the clade comparable to those reported for adaptive radiations. the calystegia clade also exhibits a high diversification rate which probably reflects rapid diversification following colonisation of western north america. the convolvuleae thus provide a striking example of the ability of temperate lineages to rapidly colonise highly disjunct areas worldwide and to diversify. 
in keeping with other temperate lineages exhibiting disjunct distributions, long-distance dispersal is inferred as the main process explaining the patterns observed although for one american-eurasian disjunction we cannot exclude vicariance. eight major disjunctions are observed in convolvuleae: two northern hemisphere, two southern hemisphere and four amphitropical. diversity in the southern hemisphere is largely the result of a single colonisation of africa –  ma, and subsequent dispersals from africa to both australasia and south america. speciation rates within this monophyletic, largely southern hemisphere group are found to be over twice those of the tribe as a whole. we specifically determine the number and timing of amphitropical and transoceanic disjunctions, investigate the extent to which disjunctions in convolvuleae are spatio-temporally congruent with those in other temperate plant groups and determine the impact of long-distance dispersal events on diversification rates. the convolvuleae has colonised every continent of the world with a temperate biome in c. myr and eight major range disjunctions underlie this broad distribution. the colonisation of the temperate zones of the three southern continents within the last c. myr is likely to have stimulated high rates of diversification recovered in this group, with lineage accumulation rates comparable to those reported for adaptive radiations. increased speciation rates are also observed in calystegia. this paper aims to investigate how the world’s disjunct temperate zones have been colonised by the pan-temperate plant group convolvuleae, sampling of the c. known species.
 at a global scale, the temperate zone is highly fragmented both between and within hemispheres. this paper aims to investigate how the world’s disjunct temperate zones have been colonised by the pan-temperate plant group convolvuleae, sampling of the c. known species. we specifically determine the number and timing of amphitropical and transoceanic disjunctions, investigate the extent to which disjunctions in convolvuleae are spatio-temporally congruent with those in other temperate plant groups and determine the impact of long-distance dispersal events on diversification rates.  eight major disjunctions are observed in convolvuleae: two northern hemisphere, two southern hemisphere and four amphitropical. diversity in the southern hemisphere is largely the result of a single colonisation of africa –  ma, and subsequent dispersals from africa to both australasia and south america. speciation rates within this monophyletic, largely southern hemisphere group are found to be over twice those of the tribe as a whole. increased speciation rates are also observed in calystegia.  the convolvuleae has colonised every continent of the world with a temperate biome in c. myr and eight major range disjunctions underlie this broad distribution. in keeping with other temperate lineages exhibiting disjunct distributions, long-distance dispersal is inferred as the main process explaining the patterns observed although for one american-eurasian disjunction we cannot exclude vicariance. the colonisation of the temperate zones of the three southern continents within the last c. myr is likely to have stimulated high rates of diversification recovered in this group, with lineage accumulation rates comparable to those reported for adaptive radiations. electronic supplementary material the online version of this article contains supplementary material, which is available to authorized users. keywords amphitropicalcalystegiaconvolvulusdisjunctiondiversification ratespolymeriatemperatetransoceanicissue-copyright-statement© the author 2016 