BACKGROUND
the taxonomic status of the african elephant  has been debated since the turn of the 20th century  <cit>  and up to  <dig> subspecies have been described  <cit> .
however, modern taxonomy refers to two types, with their names reflecting the habitat in which they are found, namely the larger savannah   and the smaller forest   elephants.
it has become increasingly established in the literature that forest and savannah elephants are distinct species   <cit> , with recent publications considering their datasets in the light of this concept.
the most persuasive genetic basis for a two-taxon model originates from a series of studies exploring patterns of differentiation at nuclear loci, culminating in a study using male inherited y-chr, andbi-parentally inherited x-chr sequences  <cit>  that concluded "there was a deep and almost complete separation between african forest and african savannah elephants."
in this study, divergent nuclear dna sequences segregated with either forest or savannah elephant morphological types.
there were, however, a number of exceptions, including a forest elephant from garamba in the democratic republic of congo  that had nuclear sequences typical of savannah elephants and two savannah elephants from cameroon  that had nuclear sequences typical of forest elephants  <cit> .
the study estimated the divergence between the savannah and forest elephants to be  <dig> million years.
the two-taxon argument has also been used to explain data from two nuclear microsatellite dna  <cit>  and one morphological study  <cit> .
however, subsequently debruyne  <cit>  performed a morphometric analysis of museum elephant skulls, and found evidence for a continuum between two morphotypes, suggesting that, despite historical separation that promoted subdivision, these two forms freely interbreed wherever their ranges intersect.
molecular studies using mitochondrial  dna  <cit>  including data from the study by roca et al  <cit>  have pointed to a more complex scenario for african elephants.
debruyne  <cit>  examined several thousand base pairs of mtdna from elephants across africa and although he also reported two highly divergent molecular clades, these did not conform to the morphological delineations of cyclotis and africana.
he interpreted these results as a consequence of incomplete isolation between forest and savannah african elephant populations, followed by recurrent and ongoing introgression between the two forms.
roca et al.
<cit>  obtained very similar mitochondrial results but explained the non-concordance between mitochondrial and nuclear markers as a result of cytonuclear genomic disassociation such that the mitochondrial tree did not reflect the species tree.
the mtdna results observed were explained as having arisen during episodes of backcrossing between successive generations of savannah males with forest females, leading to half of extant savannah elephants surveyed possessing 'forest' typical mitochondrial haplotypes but almost exclusively 'savannah' nuclear x and y-chromosomal dna.
eggert et al.
<cit>   included samples from west africa and found a more complex picture using mtdna and nuclear microsatellites, suggesting that western savannah and forest elephants formed a potential third loxodonta taxonomic unit.
finally, roca et al.
<cit> recently revisited the question with a statistical re-analysis of eight morphological and genetic datasets  including their own and those of eggert et al.
<cit>  and debruyne  <cit>  and reconfirmed their initial interpretation of a two taxon model with cyto-nuclear genomic dissociation.
the above-mentioned studies largely share a pronounced lack of forest elephant data.
the nuclear dna studies  <cit>  featured limited sampling from central african forest elephants.
despite describing a narrow hybrid zone between the two elephant types, only one population located in this zone ) was included and none from elsewhere in drc or from west central africa were examined.
elsewhere, debruyne  <cit>  included elephants from across drc in his study but was again limited by sample size.
the study by eggert et al.
<cit>  was limited by the inclusion of only two populations of central african forest elephants, both from the edge of the forest range in cameroon which may conceivably have influenced their conclusion of the genetic uniqueness of forest and western elephants.
to date, no study has addressed the partitioning of genetic diversity in the equatorial forests of africa.
further, the potential effect of pleistocene forest refugia was partially addressed by eggert et al.
<cit>  and also previously reported as having a major influence on large mammal distribution and range dynamics  <cit>  has yet to be addressed in african elephants.
here we report results from the most extensive sample of forest elephants to date, from the core of their range, and compare these results with previously published mitchondrial dna sequences for savannah elephants from east and southern africa and populations from west africa and drc.
we examined the phylogeographic history, population structure and past demography of african elephants using patterns of molecular diversity for the mtdna control region and cytochrome b gene.
since mtdna is maternally inherited, this marker provides a female-biased view of population history and structure.
we included the most variable mtdna segment, the hypervariable region  <dig>  of the control region since it has a high rate of nucleotide change, allowing recently diverged lineages to be distinguished  <cit> .
this segment is equivalent to data previously published by eggert et al.
<cit>  and debruyne  <cit> , allowing us to examine forest elephant sequences within the context of a sample set with the largest geographic coverage.
we could not use roca's mtdna sequences as he studied a different fragment .
RESULTS
central forest samples
we sequenced  <dig> bp of hvr <dig> of the control region from  <dig> samples and  <dig> bp of the cytochrome b from  <dig>  no nuclear copies of mitochondrial dna  were detected for either sequence.
combined sequences
genetic diversity
for hvr <dig>  we analysed  <dig> sequences from  <dig> sites across africa in both forest and savannah elephants .
of these  <dig> were from forest elephants  and  <dig> savannah elephants .
the combined dataset comprised eighty-eight haplotypes  and four haplotypes found in both types.
of the  <dig> central african forest elephant haplotypes identified in this study,  <dig> were novel .
mean nucleotide diversity  for hvr <dig> sequences for all african elephants was  <dig>  , while mean haplotype diversity  was  <dig>  .
when haplotypes were divided into forest and savannah, based on prior designation, the forest population π was  <dig>  , significantly lower than for savannah elephants .
the mean haplotype diversity for forest and savannah populations was  <dig>   and  <dig>  , respectively.
the lowest nucleotide diversity of all groupings was for the new central african forest samples in this study , while haplotype diversity was  <dig>  .
for cytochrome b,  <dig> sequences were analysed,  <dig> from this study,  <dig> provided by sn and  <dig> from genbank.
forty-four haplotypes were identified including three and  <dig> new forest and savannah elephant sequences, respectively .
of the  <dig> haplotypes,  <dig> were found in savannah elephants and  <dig> in forest elephants, with two haplotypes found in both.
mean π for cytochrome b was  <dig>   for all elephants.
when forest and savannah elephants were subdivided, π was again significantly lower for forest populations  than for savannah populations .
these results contrast with the study of roca et al.
who reported  <dig> haplotypes for  <dig> elephants at the mitochondrial nd <dig> locus and described low genetic diversity as being typical for savannah elephants.
population structure
the median joining networks for the hvr <dig> and cytochrome b sequences , exhibit patterns consistent with a complex demographic history.
the hvr <dig> pattern is more complex  than for cytochrome b .
haplotype designations for this and previous studies for both sequences are found in table  <dig>  and table  <dig> .
for the hvr <dig> region, the most obvious feature is that central african forest elephants  fall into two separate groups  with little geographic structuring, consisting of  <dig>  and  <dig>  haplotypes with variable frequencies.
only two forest elephants from drc, share the same haplotype with other forest elephants in hvr <dig> haplogroup ii.
the remaining seven drc forest elephant haplotypes , group with sequences in hvr <dig> haplogroup iii .
the other striking feature is that for west african elephants , both forest and savannah types possess haplotypes found almost exclusively within the same haplogroup as central african forest elephants .
twenty-five out of  <dig> haplotypes from west africa are more closely related to central forest elephants from gabon, congo and car.
a single western savannah sequence  can be found in hvr <dig> haplogroup iv grouping with savannah elephants from eastern, southern and central africa.
analysis of molecular variance  of hvr <dig> sequences revealed a non-significant  genetic structure  when populations were grouped according to geographic distribution .
* original name from each author .
* original name from each author  ** sample sharing both, forest and savannah haplotypes, according to the author .
as expected, cytochrome b is less variable than hvr <dig>  however, direct comparison between patterns obtained from both regions is compromised here due to a lack of equivalent individuals examined at both loci, specifically for savannah elephants.
however the overall pattern when individuals from different populations were examined is consistent with the pattern obtained with hvr <dig>  despite the resolution of only three haplogroups as opposed to four.
savannah elephant haplotypes fall into two distinct haplogroups  as do forest elephant haplotypes .
cytochrome b haplogroup ii, which is divided into two haplogroups for hvr <dig>  is characterised by a network structure in which forest and savannah elephant samples are not overlaid .
again all western elephants, both forest and savannah, cluster with central african forest elephants .
demographic history
when hvr <dig> sequences from forest and savannah elephants were examined separately, fu's fs was - <dig>   and - <dig>  , respectively.
although significant values can indicate historical population expansion, the multimodal pattern  for the forest elephant groups suggests that these populations encompass several subgroups as indicated in the networks.
when we examined each haplogroup separately for signatures of demographic change , a smooth and predominantly unimodal pattern was observed for hvr <dig> haplogroup i, indicating a recent demographic expansion , while hvr <dig> haplogroups ii, iii and iv were more complex, including the presence of some divergent haplotypes.
discussion
in the light of the results obtained with the mitochondrial sequences used here, additional interpretations of the history of african elephants become evident and suggest that the conclusions drawn in previous studies may have been hampered by incomplete sample sets.
forest elephants have been affected by cyclical climatic changes that occurred over the last  <dig>  million years as the colder drier periods experienced during pleistocene glacial maxima are believed to have led to the repeated retraction of forest cover into refugial zones followed by re-expansion, fostering allopatric divergence between isolated populations  <cit>  and secondary contact.
the forest elephant range is therefore likely to have become centred around such refugia on several occasions.
the dataset presented here raises the possibility of at least two different refugia in the central african region harbouring distinct elephant populations that diverged allopatrically.
if this was the case, forest elephants possessing distinct mitochondrial genotypes are likely to have come into contact relatively rapidly after the end of the last glaciation , when the forests re-expanded  <cit> .
such a scenario might explain not only the two haplogroups present in forest elephants but also the lower nucleotide diversity that characterises elephant populations found in forest habitat.
this scenario might also explain the high microsatellite diversity reported for forest elephants  <cit> .
if several populations diverged in isolation, accumulating different microsatellite profiles, and subsequently became sympatric as the forest expanded, the large single population that today comprises two central african forest elephant lineages might be expected to have engendered higher microsatellite diversity.
savannah populations, especially those in the south and east, would not have been affected by forest expansion since these areas remained unforested and thus habitat would not have been lost.
those savannah populations that may have been affected are those that may have occurred in areas that subsequently became forested.
one explanation for the close genetic proximity between forest and savannah genotypes in drc could be introgression between savannah haplotypes into forest genomes as forests expanded and savannah habitat was lost.
such introgression would be in the opposite direction to that proposed by roca et al.
<cit> .
the results obtained for elephants in west and central africa have strong implications for the division of elephants into forest and savannah species.
these elephants are taxonomically indeterminate  <cit>  and have been described as having an intermediate morphology  <cit> .
mitochondrially, west african elephants are found in the same haplogroups as the  forest elephant lineages of central africa.
if ancient female-mediated introgression between the two forms followed by backcrossing into savannah populations is the reason why western savannah elephants possess largely 'forest' haplotypes then nuclear markers at these loci should resemble predominantly those of southern and eastern savannah elephants today.
alternatively these elephant populations could be an example of protracted gene flow between two forms of elephant, which is ongoing  and that west african savannah elephants are not distinguishable at the genetic or morphological level from their forest counterparts .
a third explanation could be a 'second movement' of elephants out of the forest  and into the savannah.
there are insufficient data to determine whether there was a single movement from forest to savannah habitat or whether these were multiple events, precipitating the morphological changes observed today.
whatever the origin of the two types, our data would support continued extensive hybridisation between the two proposed forms.
CONCLUSIONS
our mitochondrial analysis does not support the simple separation of modern african elephants into two groups.
the evidence is most clear in west africa where savannah elephants are indistinguishable at both the mitochondrial and morphological level from their forest counterparts.
the two species model cannot be easily applied in this region and neither do west african elephants represent a third distinct entity.
central african elephant populations west of the congo river also question the current classification.
forest elephants fall into two major groupings with mitochondrial dna.
previous studies found two major groups for all african elephants, savannah and savannah/forest perhaps suggesting ancient introgression between forest females and savannah males in the past.
however the inclusion of a larger central forest sample in this study would suggest that this explanation is too simple and that african elephants were subject to a more complex demographic history.
phylogenetic and phylogeographic reanalysis of species is important for many reasons but with the massive extinction of species in the wild in the last  <dig> years accurate descriptions are essential for management of wild resources.
for elephants, the classification of species into savannah and forest may not reflect their evolutionary history but simply the habitat in which they currently exist.
while ecotypic differentiation has been shown to be the predominant factor driving molecular divergence in one widely distributed african herbivore recently  <cit> , this may not apply in elephants and if it does, may not conform to a simple forest versus savannah habitat driven divergence.
to develop management strategies incorporating a simple forest/savannah model could be misleading until further lines of evidence give us a clearer picture of the origins and current conservation needs of elephants populations throughout the continent.
future studies should analyse nuclear dna markers, including those which evolve rapidly, across the range of forest and savannah elephants and especially in transition zones to investigate this complex ongoing process further.

 the taxonomic status of the african elephant has been debated since the turn of the 20th century and up to subspecies have been described. however, modern taxonomy refers to two types, with their names reflecting the habitat in which they are found, namely the larger savannah and the smaller forest elephants. it has become increasingly established in the literature that forest and savannah elephants are distinct species, with recent publications considering their datasets in the light of this concept. the most persuasive genetic basis for a two-taxon model originates from a series of studies exploring patterns of differentiation at nuclear loci, culminating in a study using male inherited y-chr, andbi-parentally inherited x-chr sequences that concluded "there was a deep and almost complete separation between african forest and african savannah elephants." in this study, divergent nuclear dna sequences segregated with either forest or savannah elephant morphological types. there were, however, a number of exceptions, including a forest elephant from garamba in the democratic republic of congo that had nuclear sequences typical of savannah elephants and two savannah elephants from cameroon that had nuclear sequences typical of forest elephants. the study estimated the divergence between the savannah and forest elephants to be million years. the two-taxon argument has also been used to explain data from two nuclear microsatellite dna and one morphological study. however, subsequently debruyne performed a morphometric analysis of museum elephant skulls, and found evidence for a continuum between two morphotypes, suggesting that, despite historical separation that promoted subdivision, these two forms freely interbreed wherever their ranges intersect. molecular studies using mitochondrial dna including data from the study by roca et al have pointed to a more complex scenario for african elephants. debruyne examined several thousand base pairs of mtdna from elephants across africa and although he also reported two highly divergent molecular clades, these did not conform to the morphological delineations of cyclotis and africana. he interpreted these results as a consequence of incomplete isolation between forest and savannah african elephant populations, followed by recurrent and ongoing introgression between the two forms. roca et al. obtained very similar mitochondrial results but explained the non-concordance between mitochondrial and nuclear markers as a result of cytonuclear genomic disassociation such that the mitochondrial tree did not reflect the species tree. the mtdna results observed were explained as having arisen during episodes of backcrossing between successive generations of savannah males with forest females, leading to half of extant savannah elephants surveyed possessing'forest' typical mitochondrial haplotypes but almost exclusively'savannah' nuclear x and y-chromosomal dna. eggert et al. included samples from west africa and found a more complex picture using mtdna and nuclear microsatellites, suggesting that western savannah and forest elephants formed a potential third loxodonta taxonomic unit. finally, roca et al. recently revisited the question with a statistical re-analysis of eight morphological and genetic datasets including their own and those of eggert et al. and debruyne and reconfirmed their initial interpretation of a two taxon model with cyto-nuclear genomic dissociation. the above-mentioned studies largely share a pronounced lack of forest elephant data. the nuclear dna studies featured limited sampling from central african forest elephants. despite describing a narrow hybrid zone between the two elephant types, only one population located in this zone ) was included and none from elsewhere in drc or from west central africa were examined. elsewhere, debruyne included elephants from across drc in his study but was again limited by sample size. the study by eggert et al. was limited by the inclusion of only two populations of central african forest elephants, both from the edge of the forest range in cameroon which may conceivably have influenced their conclusion of the genetic uniqueness of forest and western elephants. to date, no study has addressed the partitioning of genetic diversity in the equatorial forests of africa. further, the potential effect of pleistocene forest refugia was partially addressed by eggert et al. and also previously reported as having a major influence on large mammal distribution and range dynamics has yet to be addressed in african elephants. here we report results from the most extensive sample of forest elephants to date, from the core of their range, and compare these results with previously published mitchondrial dna sequences for savannah elephants from east and southern africa and populations from west africa and drc. we examined the phylogeographic history, population structure and past demography of african elephants using patterns of molecular diversity for the mtdna control region and cytochrome b gene. since mtdna is maternally inherited, this marker provides a female-biased view of population history and structure. we included the most variable mtdna segment, the hypervariable region of the control region since it has a high rate of nucleotide change, allowing recently diverged lineages to be distinguished. this segment is equivalent to data previously published by eggert et al. and debruyne, allowing us to examine forest elephant sequences within the context of a sample set with the largest geographic coverage. we could not use roca's mtdna sequences as he studied a different fragment.  central forest samples we sequenced bp of hvr of the control region from samples and bp of the cytochrome b from no nuclear copies of mitochondrial dna were detected for either sequence. combined sequences genetic diversity for hvr we analysed sequences from sites across africa in both forest and savannah elephants. of these were from forest elephants and savannah elephants. the combined dataset comprised eighty-eight haplotypes and four haplotypes found in both types. of the central african forest elephant haplotypes identified in this study, were novel. mean nucleotide diversity for hvr sequences for all african elephants was, while mean haplotype diversity was. when haplotypes were divided into forest and savannah, based on prior designation, the forest population π was, significantly lower than for savannah elephants. the mean haplotype diversity for forest and savannah populations was and, respectively. the lowest nucleotide diversity of all groupings was for the new central african forest samples in this study, while haplotype diversity was. for cytochrome b, sequences were analysed, from this study, provided by sn and from genbank. forty-four haplotypes were identified including three and new forest and savannah elephant sequences, respectively. of the haplotypes, were found in savannah elephants and in forest elephants, with two haplotypes found in both. mean π for cytochrome b was for all elephants. when forest and savannah elephants were subdivided, π was again significantly lower for forest populations than for savannah populations. these results contrast with the study of roca et al. who reported haplotypes for elephants at the mitochondrial nd locus and described low genetic diversity as being typical for savannah elephants. population structure the median joining networks for the hvr and cytochrome b sequences, exhibit patterns consistent with a complex demographic history. the hvr pattern is more complex than for cytochrome b. haplotype designations for this and previous studies for both sequences are found in table and table. for the hvr region, the most obvious feature is that central african forest elephants fall into two separate groups with little geographic structuring, consisting of and haplotypes with variable frequencies. only two forest elephants from drc, share the same haplotype with other forest elephants in hvr haplogroup ii. the remaining seven drc forest elephant haplotypes, group with sequences in hvr haplogroup iii. the other striking feature is that for west african elephants, both forest and savannah types possess haplotypes found almost exclusively within the same haplogroup as central african forest elephants. twenty-five out of haplotypes from west africa are more closely related to central forest elephants from gabon, congo and car. a single western savannah sequence can be found in hvr haplogroup iv grouping with savannah elephants from eastern, southern and central africa. analysis of molecular variance of hvr sequences revealed a non-significant genetic structure when populations were grouped according to geographic distribution. * original name from each author. * original name from each author ** sample sharing both, forest and savannah haplotypes, according to the author. as expected, cytochrome b is less variable than hvr however, direct comparison between patterns obtained from both regions is compromised here due to a lack of equivalent individuals examined at both loci, specifically for savannah elephants. however the overall pattern when individuals from different populations were examined is consistent with the pattern obtained with hvr despite the resolution of only three haplogroups as opposed to four. savannah elephant haplotypes fall into two distinct haplogroups as do forest elephant haplotypes. cytochrome b haplogroup ii, which is divided into two haplogroups for hvr is characterised by a network structure in which forest and savannah elephant samples are not overlaid. again all western elephants, both forest and savannah, cluster with central african forest elephants. demographic history when hvr sequences from forest and savannah elephants were examined separately, fu's fs was - and -, respectively. although significant values can indicate historical population expansion, the multimodal pattern for the forest elephant groups suggests that these populations encompass several subgroups as indicated in the networks. when we examined each haplogroup separately for signatures of demographic change, a smooth and predominantly unimodal pattern was observed for hvr haplogroup i, indicating a recent demographic expansion, while hvr haplogroups ii, iii and iv were more complex, including the presence of some divergent haplotypes. discussion in the light of the results obtained with the mitochondrial sequences used here, additional interpretations of the history of african elephants become evident and suggest that the conclusions drawn in previous studies may have been hampered by incomplete sample sets. forest elephants have been affected by cyclical climatic changes that occurred over the last million years as the colder drier periods experienced during pleistocene glacial maxima are believed to have led to the repeated retraction of forest cover into refugial zones followed by re-expansion, fostering allopatric divergence between isolated populations and secondary contact. the forest elephant range is therefore likely to have become centred around such refugia on several occasions. the dataset presented here raises the possibility of at least two different refugia in the central african region harbouring distinct elephant populations that diverged allopatrically. if this was the case, forest elephants possessing distinct mitochondrial genotypes are likely to have come into contact relatively rapidly after the end of the last glaciation, when the forests re-expanded. such a scenario might explain not only the two haplogroups present in forest elephants but also the lower nucleotide diversity that characterises elephant populations found in forest habitat. this scenario might also explain the high microsatellite diversity reported for forest elephants. if several populations diverged in isolation, accumulating different microsatellite profiles, and subsequently became sympatric as the forest expanded, the large single population that today comprises two central african forest elephant lineages might be expected to have engendered higher microsatellite diversity. savannah populations, especially those in the south and east, would not have been affected by forest expansion since these areas remained unforested and thus habitat would not have been lost. those savannah populations that may have been affected are those that may have occurred in areas that subsequently became forested. one explanation for the close genetic proximity between forest and savannah genotypes in drc could be introgression between savannah haplotypes into forest genomes as forests expanded and savannah habitat was lost. such introgression would be in the opposite direction to that proposed by roca et al.. the results obtained for elephants in west and central africa have strong implications for the division of elephants into forest and savannah species. these elephants are taxonomically indeterminate and have been described as having an intermediate morphology. mitochondrially, west african elephants are found in the same haplogroups as the forest elephant lineages of central africa. if ancient female-mediated introgression between the two forms followed by backcrossing into savannah populations is the reason why western savannah elephants possess largely'forest' haplotypes then nuclear markers at these loci should resemble predominantly those of southern and eastern savannah elephants today. alternatively these elephant populations could be an example of protracted gene flow between two forms of elephant, which is ongoing and that west african savannah elephants are not distinguishable at the genetic or morphological level from their forest counterparts. a third explanation could be a'second movement' of elephants out of the forest and into the savannah. there are insufficient data to determine whether there was a single movement from forest to savannah habitat or whether these were multiple events, precipitating the morphological changes observed today. whatever the origin of the two types, our data would support continued extensive hybridisation between the two proposed forms.  our mitochondrial analysis does not support the simple separation of modern african elephants into two groups. the evidence is most clear in west africa where savannah elephants are indistinguishable at both the mitochondrial and morphological level from their forest counterparts. the two species model cannot be easily applied in this region and neither do west african elephants represent a third distinct entity. central african elephant populations west of the congo river also question the current classification. forest elephants fall into two major groupings with mitochondrial dna. previous studies found two major groups for all african elephants, savannah and savannah/forest perhaps suggesting ancient introgression between forest females and savannah males in the past. however the inclusion of a larger central forest sample in this study would suggest that this explanation is too simple and that african elephants were subject to a more complex demographic history. phylogenetic and phylogeographic reanalysis of species is important for many reasons but with the massive extinction of species in the wild in the last years accurate descriptions are essential for management of wild resources. for elephants, the classification of species into savannah and forest may not reflect their evolutionary history but simply the habitat in which they currently exist. while ecotypic differentiation has been shown to be the predominant factor driving molecular divergence in one widely distributed african herbivore recently, this may not apply in elephants and if it does, may not conform to a simple forest versus savannah habitat driven divergence. to develop management strategies incorporating a simple forest/savannah model could be misleading until further lines of evidence give us a clearer picture of the origins and current conservation needs of elephants populations throughout the continent. future studies should analyse nuclear dna markers, including those which evolve rapidly, across the range of forest and savannah elephants and especially in transition zones to investigate this complex ongoing process further. 
we analysed hypervariable region of the mitochondrial control region for new central african forest elephants and the mitochondrial cytochrome b gene from new samples and compare these sequences to other african elephant data. we find that central african forest elephant populations fall into at least two lineages and that west african elephants share their mitochondrial history almost exclusively with central african forest elephants. we also find that central african forest populations show lower genetic diversity than those in savannahs, and infer a recent population expansion. previous phylogenetic analyses of african elephants have included limited numbers of forest elephant samples. a large-scale assessment of mitochondrial dna diversity in forest elephant populations here reveals a more complex evolutionary history in african elephants as a whole than two-taxon models assume. our data do not support the separation of african elephants into two evolutionary lineages. the demographic history of african elephants seems more complex, with a combination of multiple refugial mitochondrial lineages and recurrent hybridization among them rendering a simple forest/savannah elephant split inapplicable to modern african elephant populations.
 previous phylogenetic analyses of african elephants have included limited numbers of forest elephant samples. a large-scale assessment of mitochondrial dna diversity in forest elephant populations here reveals a more complex evolutionary history in african elephants as a whole than two-taxon models assume.  we analysed hypervariable region of the mitochondrial control region for new central african forest elephants and the mitochondrial cytochrome b gene from new samples and compare these sequences to other african elephant data. we find that central african forest elephant populations fall into at least two lineages and that west african elephants share their mitochondrial history almost exclusively with central african forest elephants. we also find that central african forest populations show lower genetic diversity than those in savannahs, and infer a recent population expansion.  our data do not support the separation of african elephants into two evolutionary lineages. the demographic history of african elephants seems more complex, with a combination of multiple refugial mitochondrial lineages and recurrent hybridization among them rendering a simple forest/savannah elephant split inapplicable to modern african elephant populations. 