Abstract
The purple snail Plicopurpura pansa is a common member of the rocky intertidal community of the Tropical Eastern Pacific. It has a free-living larva that is dispersed by marine currents. We analyzed the demographic (historic), genetic, and phylogeographic structure of P. pansa using a fragment of the cytochrome b gene (687 bp). Data were analyzed by analysis of molecular variance, nested clade analysis (NCA), and a mismatch distribution analysis under the expanding population hypothesis. A total of 219 organisms were collected from 16 localities along the Mexican Pacific coast and one in Costa Rica. We obtained a total of 92 haplotypes. Genetic differences among Mexican populations were low. The Clarión Island population was significantly different from 6 of the Mexican populations studied. This result was attributed to the fact that Clarión is an oceanic island and the currents veer offshore most of the year. Haplotype network and mismatch distribution analyses indicated that the Mexican populations are undergoing expansion. The NCA confirmed a contiguous range expansion of haplotypes and this result may be related to the time that larvae spend in marine currents and to the effect of natural barriers, such as gyres, in Central America and the Isthmus of Tehuantepec.
Highlights
Phylogeography examines the intraspecific lineage relationships throughout the species’ distribution area (Avise 2000)
A 687-bp fragment of mitochondrial cytochrome b was sequenced from each of the 216 individuals collected along 3,000 km of coastline from Pescadero, Baja California Sur, to Huatulco, Oaxaca (Fig. 1), with an extra 3 samples from Costa Rica
Rocky intertidal gastropods show different patterns of genetic diversity depending on the time larvae spend as plankton (Crandall et al 2008, Díaz-Ferguson et al 2012, Haupt et al 2013) or if they are direct developers (Ayre et al 2009, Cox et al 2014)
Summary
Phylogeography examines the intraspecific lineage relationships throughout the species’ distribution area (Avise 2000). Larval dispersal is influenced by the time larvae spend in open waters (Paulay and Meyer 2006) or whether the organisms show direct or larval development (Lee and Boulding 2009, Sánchez et al 2011) Habitat availability is another factor that affects species distribution, since organisms will settle in specific habitats along their distribution range (Kirkendale and Meyer 2004, Elligson and Krug 2006, Crandall et al 2008). Los marcadores más comunes usados para estudios de la filogeografía de gasterópodos de la zona intermareal rocosa son el citocromo c oxidasa subunidad I (COI), citocromo b ó ambos (Lee y Boulding 2007, Crandall et al 2008, Van den Broeck et al 2008, Haupt et al 2013, Espinoza et al 2015, Nuñez et al 2015). Plankton and are found in the continuous rocky intertidal habitat of the Pacific coast, with only some gaps of sandy beaches in northern Central America (Hurtado et al 2007), we expected to find ancestral haplotypes in the southern populations and derived haplotypes in the northern populations in its eastern Pacific distribution
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