Phylogenetics and molecular clocks reveal the repeated evolution of ant‐plants after the lateMiocene inAfrica and the earlyMiocene inAustralasia and theNeotropics

Abstract

SummaryAnt-plant symbioses involve over 110 ant species in five subfamilies that are facultative or obligate occupants of stem, leaf or root domatia formed by hundreds of ant-plant species. The phylogenetic distribution and geological ages of these associations, and the frequency of gains or losses of domatium, are largely unknown.We compiled an up-to-date list of ant domatium-bearing plants, estimated their probable true number from model-based statistical inference, generated dated phylogenies that include c. 50% of ant-plant lineages, and traced the occurrence of domatia and extrafloral nectaries on a 1181-species tree, using likelihood and Bayesian methods.We found 681 vascular plants with domatia (159 genera in 50 families) resulting from minimally 158 inferred domatium origins and 43 secondary losses over the last 19 Myr. The oldest African ant-plant symbioses are younger than those in Australasia and the Neotropics. The best statistical model suggests that the true number of myrmecophytes may approach 1140 species.The phylogenetic distribution of ant-plants shows that domatia evolved from a range of pre-adapted morphological structures and have been lost frequently, suggesting that domatia have no generalizable effect on diversification. The Miocene origin of ant-plant symbioses is consistent with inferred changes in diet and behaviour during ant evolution.

Macroevolutionary assembly of ant/plant symbioses:Pseudomyrmexants and their ant-housing plants in the Neotropics

“…In the plants, we inferred single gains of domatia in Vachellia (electronic supplementary material, figures S7 and S12) and Triplaris (electronic supplementary material, figures S8 and S12), confirming previous results [14], and three gains of domatia in Ruprechtia (electronic supplementary material, figures S8 and S12), at least nine in Tachigali (electronic supplementary material, figures S9 and S12) and five in Platymiscium (electronic supplementary material, figure S10 and S12). No domatium loss was inferred.…”

“…To reconstruct the evolutionary gains and losses of domatia in Vachellia, Tachigali, Triplaris/Ruprechtia and Platymiscium, we coded each tip for domatium absence (0) or domatium presence (1), using the world list of domatium-bearing plants [14]. We performed ancestral state reconstructions using the same approaches as for the Pseudomyrmecinae.…”

“…Ant/plant symbioses appear to be younger than seed dispersal by ants or extrafloral nectary-mediated plant defence by ants, with no extant domatium-bearing clade older than 20 Myr [14]. Few co-phylogenetic studies of ant/plant systems have been conducted.…”

A bioassay for measuring the intensities of ant defenses on <i>Macaranga </i>myrmecophytes

“…To date, approximately 4,000 plant species have been reported to bear extra floral nectaries to attract ants (Weber and Keeler 2013) and more than 680 plant species are known as myrmecophytes or ant-plants , which have modified structures, so-called domatia, to host specific ant species (plant-ants) (Chomicki and Renner 2015). To evaluate the effectiveness of ant defense in a plant species, it is essential to elucidate the associations between the plant and the ant species (Bronstein 1998, Heil and McKey 2003, Oliveira and Freitas 2004, Bronstein et al 2006, Rico-Gray and Oliveira 2007, Del-Claro et al 2013.…”

Protection against herbivory in the mutualism between Pseudomyrmex dendroicus (Formicidae) and Triplaris americana (Polygonaceae)

“…Myrmecophytes (i.e., plants sheltering the colonies of a limited number of 'plantant' species in hollow structures called domatia and sometimes also providing them with food in the form of extrafloral nectar and food bodies) are pervasive and very diverse in the Tropics (Chomicki and Renner 2015). This is a mutualistic association as, in return for being housed and sometimes fed, plant-ants protect their host myrmecophyte from encroaching vegetation, herbivores and pathogens, and/or provide them with nutrients (i.e., myrmecotrophy) (Rico-Gray and Oliveira 2007, Mayer et al 2014.…”