Diversification of sympatric broadcast-spawning limpets (Cellana spp.) within the Hawaiian archipelago

Abstract

Speciation remains a central enigma in biology, and nowhere is this more apparent than in shallow tropical seas where biodiversity rivals that of tropical rainforests. Obvious barriers to gene flow are few and most marine species have a highly dispersive larval stage, which should greatly decrease opportunities for speciation via geographic isolation. The disparity in the level of geographic isolation for terrestrial and marine species is exemplified in Hawai'i where opportunities for allopatric speciation abound in the terrestrial realm. In contrast, marine colonizers of Hawai'i are believed to produce only a single endemic species or population, due to the lack of isolating barriers. To test the assertion that marine species do not diversify within Hawai'i, we examine the evolutionary origin of three endemic limpets (Cellana exarata, C. sandwicensis and C. talcosa) that are vertically segregated across a steep ecocline on rocky shores. Analyses of three mtDNA loci (12S, 16S, COI; 1565bp) and two nDNA loci (ATPSβ, H3; 709bp) in 26 Indo-Pacific Cellana species (N=414) indicates that Hawai'i was colonized once ∼3.4-7.2Ma from the vicinity of Japan. Trait mapping demonstrates that high-shore residence is the ancestral character state, such that mid- and low-shore species are the product of subsequent diversification. The Hawaiian Cellana are the first broadcast-spawners demonstrated to have speciated within any archipelago. The habitat stratification, extensive sympatry, and evolutionary history of these limpets collectively indicate a strong ecological component to speciation and support the growing body of evidence for non-allopatric speciation in the ocean.

Patrones de diversidad y estructura genética en especies antárticas y subantárticas de Nacella (Nacellidae)

“…Tales resultados evidencian el impacto de los procesos glaciales sobre la demografía tanto en especies congenéricas antárticas y subantárticas producto de la reducción de sus tamaños poblacionales y probablemente de sus respectivas distribuciones durante los periodos más fríos del Cuaternario. Los niveles de diversidad genética en especies antárticas y subantárticas son menores que los registrados en otros patelogásteropodos templados y tropicales (Nakano & Ozawa, 2005;Bird et al 2007Bird et al , 2011, pero comparables a aquellos registrados en nacélidos de altas latitudes (Goldstien et al 2006;de Aranzamendi et al 2009de Aranzamendi et al , 2011González-Wevar et al 2011). Estos resultados permiten corroborar el impacto generado por los ciclos glaciales del Cuaternario sobre los patrones de diversidad y estructura genética en Antártica y Subantártica.…”

Comparative phylogeography of the ocean planet

“…Although a squirrel in Central Park (New York) cannot deposit progeny in Hyde Park (London), a squirrelfish is capable of dispersing on this scale (48). This difference in evolutionary processes is clear in the Hawaiian Archipelago, where rare terrestrial colonists have proliferated into dozens and hundreds of species (17) whereas marine colonists produce one or a few species (104). Therefore, the evolutionary dramas above and below the waterline have the same ingredients (isolation, selection, adaptation, speciation), but markedly different tempos and outcomes (152).…”

“…For example, Hawaiian limpets of the genus Cellana have diversified within the archipelago along a tidal gradient that indicates ecological speciation (104). Certainly, species sharing population structure at unexpected locations within biogeographic provinces (such as Fiji in the tropical Pacific) (21,105), or other exceptions to those general trends, will provide evolutionary insights.…”

Surgeons and suture zones: Hybridization among four surgeonfish species in the Indo-Pacific with variable evolutionary outcomes

“…Closely related marine species often have overlapping distributions, which can obscure the role of geographic isolation in evolutionary partitioning (Bellwood and Wainwright, 2002;Rocha and Bowen, 2008). Ecological factors, on the other hand, may be a driving force behind species formation under sympatric or parapatric scenarios (Choat, 2006;Bird et al, 2011). Indeed, there are several recent examples of ecological speciation (Nosil, 2012) or speciation with gene flow (Feder et al, 2012;Abbott et al, 2013).…”