Presentation Detail

SSB Symposium: Ernst Mayr Symposium

Hembry, David [1].

Coevolution, diversification, and biogeography of a specialized insect-plant pollination mutualism on oceanic islands.

Phylogenetics has great potential to inform our understanding of coevolution at macroevolutionary scales. However, for many coevolving clades, we lack detailed knowledge of their history of diversification as well as the manner in which they assemble into patterns of interaction as they diversify. Here, I examine the co-radiation of Glochidion trees (Phyllanthaceae) and their pollinating Epicephala moths (Lepidoptera: Gracillariidae) on oceanic islands in the Pacific. Like the fig-fig wasp and yucca-yucca moth mutualisms, Epicephala moths are the sole pollinators of Glochidion trees,but the trees sacrifice a subset of their seeds to the moth larvae. Furthermore, this mutualism shows extreme reciprocal specialization, such that each Glochidion is associated with only 1-2 Epicephala and vice versa. Most Glochidion species are found in tropical Asia, but here I focus on the phylogenetics and species-specificity of the endemic co-radiation of ~25 Glochidion and their Epicephala on young (most<5 Ma) volcanic islands in southeastern Polynesia (South Pacific). I ask if Glochidion and Epicephala in southeastern Polynesia have been constrained to diversify through phylogenetic congruence and have maintained extreme reciprocal specialization. I reconstructed phylogenetic relationships among Glochidion and Epicephala using Bayesian inference and maximum likelihood and estimated divergence times using fossil, geologic, and secondary calibrations implemented in BEAST. Because island colonization is a discrete, stochastic process, I estimated the number of colonizations of southeastern Polynesia by reconstructing biogeography as a discrete-state character in BayesTraits. I used ParaFit to test for co-cladogenesis between Glochidion and Epicephala globally, and within Southeastern Polynesia. Both BayesTraits and ParaFit analyses were conducted on samples of trees, thus accommodating phylogenetic uncertainty. To examine species-specificity on three large islands, I used Bayesian phylogenetic inference and morphological diagnosis. I find that (a) Glochidion and Epicephala colonized southeastern Polynesia multiple times, but not congruently (b) the second colonization by Epicephala spread across twelve Glochidion species in three archipelagos very rapidly (perhaps <1 Ma) (c) Glochidion and Epicephala show phylogenetic congruence globally but not within southeastern Polynesia and(d) insular Glochidion-Epicephala networks are less specialized than those in Asia. These findings indicate that the reciprocal specialization observed in this mutualism in continental regions does not prevent the evolution of reduced specialization and dramatic host-shifts on young oceanic islands. Far from being constrained to diversify through strict cospeciation, patterns of interaction are highly dynamic over short evolutionary timescales, and these dynamics may play an important role in the mechanisms of diversification of coevolving clades.

1 - Kyoto University, Center for Ecological Research, 2-509-3 Hirano, Otsu, Shiga, 520-2113, Japan

Keywords:
cophylogenetics
Coevolution
Island biogeography
specialization
diversification.

Presentation Type: Symposium Presentation
Session: 210
Location: Ballroom 2/Cliff Lodge
Date: Sunday, June 23rd, 2013
Time: 9:30 AM
Number: 210005
Abstract ID:553
Candidate for Awards:Ernst Mayr Award