DOI: 10.5061/dryad.xksn02vc8
title: Plant dispersal strategies of high tropical alpine communities across the Andes

description: • Dispersal is a key ecological process that influences plant community
 assembly. Therefore, understanding whether dispersal strategies are
 associated with climate is of utmost importance, particularly in areas
 greatly exposed to climate change. We examined alpine plant communities
 located in the mountain summits of the tropical Andes across a 4000 km
 latitudinal gradient. We investigated species dispersal strategies and
 tested their association with climatic conditions and their evolutionary
 history. • We used dispersal-related traits (dispersal mode and growth
 form) to characterize dispersal strategies for 486 species recorded on 49
 mountain summits. Then we analysed the phylogenetic signal of traits and
 investigated the association between dispersal traits, phylogeny, climate
 and space using structural equation modelling and fourth-corner analysis
 together with RLQ ordination. • A median of 36% species in the communities
 were anemochorous (wind-dispersed) and herbaceous. This dispersal strategy
 was followed by the barochory-herb combination (herbaceous with
 unspecialised seeds, dispersed by gravity) with a median of 26.3% species
 in the communities. The latter strategy was common among species with
 distributions restricted to alpine environments. • While trait states were
 phylogenetically conserved, they were significantly associated with a
 temperature gradient. Low minimum air temperatures, found at higher
 latitudes/elevations, were correlated with the prevalence of barochory and
 the herb growth form, traits that are common among Caryophyllales,
 Brassicaceae and Poaceae. Milder temperatures, found at lower
 latitudes/elevations, were associated with endozoochorous, shrub species
 mostly from the Ericaceae family. Anemochorous species were found all
 along the temperature gradient, possibly due to the success of
 anemochorous Compositae species in alpine regions. We also found that
 trait state dominance was more associated with the climatic conditions of
 the summit than with community phylogenetic structure. Although the
 evolutionary history of the tropical Andean flora has also shaped
 dispersal strategies, our results suggest that the environment had a more
 predominant role. • Synthesis: We showed that dispersal related traits are
 strongly associated with a gradient of minimum air temperatures in the
 Andes. Global warming may weaken this key filter at tropical alpine
 summits, potentially altering community dispersal strategies in this
 region and thus, plant community structure and composition.
description: We collected information of two traits associated with plant
 dispersal strategies, namely dispersal mode and growth form. These traits
 have been identified as key traits in determining plant dispersal
 distances (Tamme et al., 2014). Given that species could have more than
 one trait category (trait state), we built species vs traits matrix as
 multi-choice nominal variables for each trait (Pavoine, Baguette,
 & Bonsall, 2010). <strong>Dispersal
 mode</strong> Based on the morphology of their
 diaspores, we assigned each species a dispersal mode: (1) anemochory, (2)
 ballochory, (3) barochory, (4) endozoochory, (5) epizoochory, and (6)
 hydrochory. Dispersal mode was obtained from the literature and from
 direct observation of diaspores of herbarium specimens when fruits and
 seeds were available. We checked references where traits for different
 groups of high Andean species were studied (Cárdenas-Arévalo &
 Vargas, 2008; Frantzen & Bouman, 1989; Melcher, Bouman, &
 Cleef, 2000, 2004; Meneses, Beck, & Anthelme, 2016) but also
 original species descriptions, taxonomic publications, flora websites and
 flora publications (92 references). We searched specimens of our
 species in five different herbaria: Universidad Nacional Mayor de San
 Marcos, Museo de Historia Natural (USM), Lima, Peru Universidad Nacional de Cajamarca
 (CPUN), Cajamarca, Peru Herbario Nacional de Bolivia,
 Universidad Mayor de San Andrés (LPB), La Paz, Bolivia Royal Botanic Gardens Kew (K),
 Richmond, UK Naturalis Biodiversity Center
 (AMD, L & U), Leiden, The Netherlands We found 220 specimens
 representing 206 of our species that had fruits/seeds that were examined
 to obtain the morphological description and then assigned the
 correspondent dispersal mode category following Table 1 in the main
 text. We chose to
 assign dispersal modes based on morphological characteristics of the
 diaspores to objectively assess all species. Therefore, we are excluding
 most observations from the field as this data was available for a reduced
 number of our species. In doing this, small seeds that are known to be
 dispersed by wind but lack any morphological adaptation for dispersal have
 been categorised as barochorous (unspecialized seeds) rather than
 anemochory. Previous studies have assigned these small seeds principally
 from the Poaceae family, as anemochorous (Frantzen & Bouman, 1989;
 Meneses, Beck, & Anthelme, 2016). In future studies,
 both seed size and morphological adaptations should be used to
 characterised dispersal modes, but currently we lack size/weight data for
 most of our species. We couldn’t assign dispersal mode
 with certainty for 15 species. Given that they lack apparent morphological
 adaptations, or their congeneric species were mostly barochorous we
 assumed these species were barochorous as well. For 8 species
 (<i>Bulbostylis juncoides</i>, <i>Oreobolopsis</i>
 <i>inversa</i>, <i>Oreobolus ecuadorensis</i>,
 <i>Oreobolus</i> <i>goeppingeri</i>,
 <i>Plantago orbignyana, Sisyrinchium hypsophilum, Sisyrinchium
 jamesonii, Trichophorum rigidum</i>) no apparent morphological
 adaptation was found in their diaspore description. However, detailed
 microscopic studies of congeneric species show adaptations to other
 dispersal modes. A few Cyperaceae congeneric species have thick
 parenchymatous mesocarp layer that allows them to float (hydrochory)
 (Melcher <i>et al.</i> 2000). A few congenerics of <i>P.
 orbignyana</i> produce mucilage which indicates epizoochory
 (Melcher, personal observations), but this remains to be tested for
 <i>P. orbignyana</i>. A few species of
 <i>Sisyrinchium</i> have umbilicus forming an air bubble that
 helps them to float (Goldblatt, Henrich, & Keating, 1989). In the
 absence of such details studies for our species we consider it was safer
 to assume barochory for these species. For the other 7 species
 (<i>Draba discoidea, Draba obovata, Draba pulvinata, Lachemilla
 moritziana, Poa glaberrima, Poa lepidula, Silene mandonii</i>) there
 was a predominant lack of diaspore morphological adaptations among their
 congenerics, therefore we assigned them as barochorous as well.
 <strong>Growth form</strong> We
 used four growth form categories: (1) herb, (2) shrub, (3) tree, and (4)
 epiphyte based on the Tropicos database (www.tropicos.org).
 This classification was preferred over a more detailed classification of
 Andean alpine growth forms (e.g. Ramsay & Oxley, 1997) due to data
 availability and because it matches those used by dispersal studies (e.g.
 Thomson et al., 2010).
description: <strong>Description of the fields</strong>
 family: species'
 family sp_name_BIEN2017: species name
 used in this study taxon_name_as_in_reference: taxon
 name for which trait data was collected as in the reference
 trait: trait name
 value_as_in_reference:
 trait data as in the reference standardised_trait_value:
 categories of trait values defined for this study main_reference: main reference
 from where the trait data was extracted. <strong>Notes about data
 "in embargo"</strong> Dispersal mode for 49 species is
 not give and is stated as "in embargo" in the field
 "standardised_trait_value" because the information is part of an
 unpublished on-going work (Melcher in prep.). <strong>Notes about
 references</strong> Only the main reference is
 provided in this dataset, secondary references (that include examination
 of herbarium specimens have not been provided). <strong>Notes about missing
 values</strong> We couldn’t assign dispersal mode
 with certainty for 15 species. Given that they lack apparent morphological
 adaptations, or their congeneric species were mostly barochorous we
 assumed these species were barochorous as well.  For 8 species
 (<i>Bulbostylis juncoides</i>, <i>Oreobolopsis</i>
 <i>inversa</i>, <i>Oreobolus ecuadorensis</i>,
 <i>Oreobolus</i> <i>goeppingeri</i>,
 <i>Plantago orbignyana, Sisyrinchium hypsophilum, Sisyrinchium
 jamesonii, Trichophorum rigidum</i>) no apparent morphological
 adaptation was found in their diaspore description. However, detailed
 microscopic studies of congeneric species show adaptations to other
 dispersal modes. A few Cyperaceae congeneric species have thick
 parenchymatous mesocarp layer that allows them to float (hydrochory)
 (Melcher <i>et al.</i> 2000). A few congenerics of <i>P.
 orbignyana</i> produce mucilage which indicates epizoochory
 (Melcher, personal observations), but this remains to be tested for
 <i>P. orbignyana</i>. A few species of
 <i>Sisyrinchium</i> have umbilicus forming an air bubble that
 helps them to float (Goldblatt, Henrich, & Keating, 1989). In the
 absence of such details studies for our species we consider it was safer
 to assume barochory for these species. For the other 7 species
 (<i>Draba discoidea, Draba obovata, Draba pulvinata, Lachemilla
 moritziana, Poa glaberrima, Poa lepidula, Silene mandonii</i>) there
 was a predominant lack of diaspore morphological adaptations among their
 congenerics, therefore we assigned them as barochorous as well.