Speciation, Divergence, and the Origin of Gryllus rubens: Behavior, Morphology, and Molecules.

David A Gray

doi:10.3390/insects2020195

Abstract

The last 25 years or so has seen a huge resurgence of interest in speciation research. This has coincided with the development and widespread use of new tools in molecular genetics, especially DNA sequencing, to inform ecological and evolutionary questions. Here I review about a decade of work on the sister species of field crickets Gryllus texensis and G. rubens. This work has included analysis of morphology, behavior, and the mitochondrial DNA molecule. The molecular work in particular has dramatically re-shaped my interpretation of the speciational history of these taxa, suggesting that rather than ‘sister’ species we should consider these taxa as ‘mother-daughter’ species with G. rubens derived from within a subset of ancestral G. texensis.

Highlights

The process of speciation remains one the central issues in evolutionary biology
(1) G. rubens had far lower genetic variation than G. texensis, (2) G. texensis sequences could be divided into two mostly discrete groups, (3) G. rubens sequences were mostly nested within one subset of the G. texensis sequences, (4) that G. rubens, but not G. texensis, showed indications of both recent population expansion and isolation by distance, and (5) that recent hybridization/gene flow is an unlikely explanation for the observed lack of reciprocal gene tree monophyly
The molecular genetic data to date have dramatically changed my interpretation of speciation between these taxa

Summary

Introduction

The process of speciation remains one the central issues in evolutionary biology. Evolution by natural selection (inclusive of sexual selection) was generally considered to be such a slow process that intrinsically historical research agendas, such as speciation, were considered nearly intractable. Today it would be almost inconceivable to study speciation without molecular data bolstering interpretations of host shifts [12,13], sympatry [14,15], and/or adaptive genetic divergence [16,17]. I will indulge in far more speculation than is typically allowed in publications of primary scientific data sets. Many of those speculations will one day be tested, whether shown to be correct or not. I hope that other researchers, including graduate students and postdocs (especially those savvy with advanced molecular techniques) find this system worthy of their time and study

Reproductive Behavior

Eco-Morphological Divergence

Genetic Divergence and Species History

Conclusion and Prospects for Future Work