Extensive cryptic species diversity and fine-scale endemism in the marine red alga Portieria in the Philippines

Abstract

We investigated species diversity and distribution patterns of the marine red alga Portieria in the Philippine archipelago. Species boundaries were tested based on mitochondrial, plastid and nuclear encoded loci, using a general mixed Yule-coalescent (GMYC) model-based approach and a Bayesian multilocus species delimitation method. The outcome of the GMYC analysis of the mitochondrial encoded cox2-3 dataset was highly congruent with the multilocus analysis. In stark contrast with the current morphology-based assumption that the genus includes a single, widely distributed species in the Indo-West Pacific (Portieria hornemannii), DNA-based species delimitation resulted in the recognition of 21 species within the Philippines. Species distributions were found to be highly structured with most species restricted to island groups within the archipelago. These extremely narrow species ranges and high levels of intra-archipelagic endemism contrast with the wide-held belief that marine organisms generally have large geographical ranges and that endemism is at most restricted to the archipelagic level. Our results indicate that speciation in the marine environment may occur at spatial scales smaller than 100 km, comparable with some terrestrial systems. Our finding of fine-scale endemism has important consequences for marine conservation and management.

DNA-based species delimitation in algae

“…Molecular phylogenetic data have indeed revealed numerous cases of (closely related) species that are morphologically indistinguishable (e.g. Zuccarello & West, 2003;De Clerck et al, 2005;Fraser et al, 2009;Fucikova et al, 2011;Gutner-Hoch & Fine, 2011;Degerlund et al, 2012;Kucera & Saunders, 2012;Moniz et al, 2012;Soehner et al, 2012;Payo et al, 2013;Souffreau et al, 2013). In addition, ancient cryptic lineages have been detected in algal groups that are morphologically depauperate, exhibit stabilizing selection, or are subject to convergent evolution towards reduced morphologies, such as planktonic unicells (Saez et al, 2003;de Vargas et al, 2004;Šlapeta et al, 2006;Krienitz & Bock, 2012;Škaloud & Rindi, 2013) and seaweeds Sutherland et al, 2011).…”

Multilocus phylogeny reveals Gibsmithia hawaiiensis (Dumontiaceae, Rhodophyta) to be a species complex from the Indo-Pacific, with the proposal of G. eilatensis sp. nov.

“…Recent genetic studies have demonstrated the high degree of cryptic diversity among red algae (e.g., Freshwater et al 2010;Payo et al 2013), particularly in groups with simple morphologies like the Dumontiaceae (Saunders 2008). Phylogenetic assessments of other members of the family that included Gibsmithia hawaiiensis and G. dotyi suggested the monophyly of the genus (Sherwood et al 2010;Clarkston and Saunders 2012).…”

Multispecies coalescent delimits structure, not species

“…Because species delimitation is inextricably linked to patterns of species diversity, the models used to delimit species are not just limited to issues about species boundaries, but are also paramount to understanding the generation and dynamics of biodiversity (9)(10)(11)(12). Consequently, when the lines become blurred-delimiting species in some cases, but populations in other cases-species delimitation becomes a critical issue with ramifications across multiple fields of study, such as, for example, the estimation of diversity in macroecological studies (13)(14)(15), analyses of food webs (16), or conservation, where oversplitting of small, isolated populations based on genetic data could be detrimental (17). More fundamentally, distinguishing between species-and population-level lineages is central to understanding the speciation process itself (18,19).…”