Ants Sow the Seeds of Global Diversification in Flowering Plants

Abstract

BackgroundThe extraordinary diversification of angiosperm plants in the Cretaceous and Tertiary periods has produced an estimated 250,000–300,000 living angiosperm species and has fundamentally altered terrestrial ecosystems. Interactions with animals as pollinators or seed dispersers have long been suspected as drivers of angiosperm diversification, yet empirical examples remain sparse or inconclusive. Seed dispersal by ants (myrmecochory) may drive diversification as it can reduce extinction by providing selective advantages to plants and can increase speciation by enhancing geographical isolation by extremely limited dispersal distances.Methodology/Principal FindingsUsing the most comprehensive sister-group comparison to date, we tested the hypothesis that myrmecochory leads to higher diversification rates in angiosperm plants. As predicted, diversification rates were substantially higher in ant-dispersed plants than in their non-myrmecochorous relatives. Data from 101 angiosperm lineages in 241 genera from all continents except Antarctica revealed that ant-dispersed lineages contained on average more than twice as many species as did their non-myrmecochorous sister groups. Contrasts in species diversity between sister groups demonstrated that diversification rates did not depend on seed dispersal mode in the sister group and were higher in myrmecochorous lineages in most biogeographic regions.Conclusions/SignificanceMyrmecochory, which has evolved independently at least 100 times in angiosperms and is estimated to be present in at least 77 families and 11 000 species, is a key evolutionary innovation and a globally important driver of plant diversity. Myrmecochory provides the best example to date for a consistent effect of any mutualism on large-scale diversification.

Patterns of seed dispersal syndromes on serpentine soils: examining the roles of habitat patchiness, soil infertility and correlated functional traits

“…We were able to find dispersal syndrome data on 466 of the 511 species (Appendix 1) from published sources (Andersen 1993;Gutterman 1994;Matlack 1994;Fuller and del Moral 2003;Haugo 2006;Lengyel et al 2009;Sawyer et al 2009) and the Kew Royal Botanical Gardens Seed Information Database (Royal Botanic Gardens 2008). Species without dispersal syndrome information were dropped from the dataset.…”

Morphological Evolution in the Mulberry Family (Moraceae)

“…Large population size would reduce extinction risk and niche expansion might have led to speciation. Defensive mutualisms involving ants and plants also appear to be accompanied by accelerated diversification rates (Weber and Agrawal 2014) and plant traits that reward ants have been regarded as key innovations (Lengyel et al 2009). Understanding whether this is the case in Cecropia s. l. will require a more fully resolved phylogeny and more thorough sampling of myrmecophytes and non-myrmecophytes than in our study.…”

“…They have served as models for the study of mutualism in general (Trager et al 2010), contributing significantly to current understanding of the nature of reciprocal benefits, how benefits vary among partners, and what costs are associated with partnerships among species (Bronstein 1998). Ecological studies of ant plants have suggested that fitness advantages and the specificity of interactions might have played roles in plant diversification (Davidson and McKey 1993;Lengyel et al 2009;Weber and Agrawal 2014). However, inferred histories of myrmecophytism are often limited by the extent of systematic knowledge.…”

The mixed effects of experimental ant removal on seedling distribution, belowground invertebrates, and soil nutrients

“…Seed dispersal by ants (i.e., myrmecochory) is particularly important in that it involves hundreds of ant species and more than ten thousand plant species across many terrestrial ecosystems (Beattie and Hughes 2002, Rico-Gray and Oliveira 2007, Lengyel et al 2009). The seed dispersal patterns that ants generate shape the initial spatial distribution of plants within populations and define the context for future ecological, demographic, and genetic interactions among emerging seedlings (Kalisz et al 1999).…”