Island time and the interplay between ecology and evolution in species diversification.

Rosemary G Gillespie

doi:10.1111/eva.12302

Abstract

Research on the dynamics of biodiversity has progressed tremendously over recent years, although in two separate directions - ecological, to determine change over space at a given time, and evolutionary, to understand change over time. Integration of these approaches has remained elusive. Archipelagoes with a known geological chronology provide an opportunity to study ecological interactions over evolutionary time. Here, I focus on the Hawaiian archipelago and summarize the development of ecological and evolutionary research; I emphasize spiders because they have attributes allowing analysis of ecological affinities in concert with diversification. Within this framework, I highlight recent insights from the island chronosequence, in particular the importance of (i) selection and genetic drift in generating diversity; (ii) fusion and fission in fostering diversification; and (iii) variability upon which selection can act. Insights into biodiversity dynamics at the nexus of ecology and evolution are now achievable by integrating new tools, in particular (i) ecological metrics (interaction networks, maximum entropy inference) across the chronosequence to uncover community dynamics and (ii) genomic tools to understand contemporaneous microevolutionary change. The work can inform applications of invasion and restoration ecology by elucidating the importance of changes in abundances, interaction strengths, and rates of evolutionary response in shaping biodiversity.

Highlights

A grand challenge in understanding the origins of biodiversity is to ‘disentangle the influence of evolutionary and historical processes operating at larger spatiotemporal scales from ecological processes operating at smaller scales’ (Lessard et al 2012)
The Hawaiian Islands are well known for spectacular examples of adaptive radiation, understanding of the extent and nature of diversification has been slow: Only 1% of the known terrestrial animals in Hawaii are vertebrates (Eldredge and Evenhuis 2003), and a broad understanding of eco-evolutionary processes has been hindered by incomplete knowledge of the 99% (Box 2)
Spiders have proved useful for this work, as ecomorphological attributes are readily measurable and provide insights into adaptive radiation that result from dynamic landscapes, polymorphism, and natural selection

Summary

Introduction

A grand challenge in understanding the origins of biodiversity is to ‘disentangle the influence of evolutionary and historical processes operating at larger spatiotemporal scales from ecological processes operating at smaller scales’ (Lessard et al 2012). The first studies to employ sequencing approaches to examine the evolutionary history of Hawaiian terrestrial organisms not surprisingly used Drosophila (Desalle et al 1986), but additional molecular studies in other groups started in the early 1990s, with work on Dubautia (Baldwin et al 1990, 1991) It was during this period that a hitherto largely unknown radiation of spiders was re-discovered, that of the long-jawed orb weaving genus Tetragnatha (Croom et al 1991; Gillespie et al 1994; Holmes and Harvey 1994). The question is, how are communities responding to the new dynamic? We hope our research will provide answers to the following: (i) What is the relative importance of priority, sequence, abundance, and interaction strengths in determining response to higher rates of immigration from non-native taxa? (ii) Are non-native species functional substitutes for native species? and (iii) Can we develop viable strategies for restoration?

Conclusion

Findings

Literature cited