Abstract
Neopetrosia proxima (Porifera: Demospongiae: Haplosclerida) is described as a morphologically variable sponge common on shallow reefs of the Caribbean. However, the range of morphological and reproductive variation within putative N. proxima led us to hypothesize that such variability may be indicative of cryptic species rather than plasticity. Using DNA sequences and morphological characters we confirmed the presence of three previously undescribed species of Neopetrosia. Morphological differences of each new congener were best resolved by partial gene sequences of the mitochondrial cytochrome oxidase subunit 1 over nuclear ones (18S rRNA and 28S rRNA). Several new characters for Neopetrosia were revealed by each new species. For example, N. dendrocrevacea sp. nov. and N. cristata sp. nov. showed the presence of grooves on the surface of the sponge body that converge at the oscula, and a more disorganized skeleton than previously defined for the genus. N. sigmafera sp. nov. adds the (1) presence of sigma microscleres, (2) significantly wider/longer oxeas (>200 μm), and (3) the presence of parenchymella larvae. Sampling of conspecifics throughout several locations in the Caribbean revealed larger spicules in habitats closer to the continental shelf than those in remote island locations. Our study highlights the importance of integrating molecular and morphological systematics for the discrimination of new Neopetrosia spp. despite belonging to one of several polyphyletic groups (families, genera) within the current definition of the order Haplosclerida.
Highlights
Cryptic species have posed a challenge to taxonomy and biodiversity studies for over 300 years, but access to DNA sequencing has provided relatively simple tools to resolve species boundaries among morphologically similar species (Bickford et al, 2007; Stat et al, 2012)
cytochrome oxidase subunit 1 (COI) showed the highest resolution of sequence dissimilarity between all new congeners and confirmed our hypothesis that morphological variability was indicative of cryptic species (Fig. 1A)
We report molecular and morphological congruence of three new Neopetrosia spp. in the Caribbean
Summary
Cryptic species have posed a challenge to taxonomy and biodiversity studies for over 300 years, but access to DNA sequencing has provided relatively simple tools to resolve species boundaries among morphologically similar species (Bickford et al, 2007; Stat et al, 2012). For taxa belonging to highly diverse orders with variable growth forms and limited morphological characters, such as corals and sponges, the integration of molecular and morphological approaches can be invaluable Congruence of molecular and morphological datasets have been successful at the subclass level and have reclassified Demospongiae into subclasses Verongimorpha, Keratosa, and the Heteroscleromorpha (Borchiellini et al, 2004; Sperling, Peterson & Pisani, 2009; Cárdenas, Pérez & Boury-Esnault, 2012; Morrow & Cárdenas, 2015). The presence of siliceous megascleres (monaxons and/or tetraxons) and highly diversified microscleres as synapomorphic characters in Heteroscleromorpha were substantiated by partial nuclear gene sequences (28S rRNA and 18S rRNA) and mitochondrial gene sequence (Holmes & Blanch, 2007; Lavrov, Wang & Kelly, 2008). Mitochondrial and nuclear genes show Haplosclerida to form a well-supported divergent clade from Heteroscleromorpha (Lavrov, Wang & Kelly, 2008; Thacker et al, 2013), almost every family within Haplosclerida is polyphyletic (Redmond et al, 2011, 2013)
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