More than What Meets the Eye: Differential Spatiotemporal Distribution of Cryptic Intertidal Bangiales.

Fernanda P Cid Alda,Nelson Valdivia,Marie-Laure Guillemin

doi:10.3390/plants11050605

Abstract

Morphologically similar but genetically distinct species have been termed cryptic and most have been assumed to be ecologically similar. However, if these species co-occur at a certain spatial scale, some niche differences at finer scales should be expected to allow for coexistence. Here, we demonstrate the existence of a disjointed distribution of cryptic bladed Bangiales along spatial (intertidal elevations) and temporal (seasons) environmental gradients. Bladed Bangiales were identified and quantified across four intertidal elevations and four seasons for one year, at five rocky intertidal sites (between 39° S and 43° S) in southern Chile. Species determination was based on partial sequences of the mitochondrial cytochrome c oxidase 1 (COI) gene amplification. To assess species gross morphology, thallus shape, color, and maximum length and width were recorded. Hundreds of organisms were classified into nine Bangiales species belonging to three genera (i.e., Fuscifolium, Porphyra, and Pyropia), including five frequent (>97% of specimens) and four infrequent species. All species, except for Pyropia saldanhae, had been previously reported along the coasts of Chile. The thallus shape and color were very variable, and a large overlap of the maximum width and length supported the cryptic status of these species. Multivariate analyses showed that the main variable affecting species composition was intertidal elevation. Species such as Py. orbicularis were more abundant in low and mid intertidal zones, while others, such as Po. mumfordii and Po. sp. FIH, were principally observed in high and spray elevations. Despite all numerically dominant species being present all year long, a slight effect of seasonal variation on species composition was also detected. These results strongly support the existence of spatial niche partitioning in cryptic Bangiales along the Chilean rocky intertidal zone.

Highlights

Differences in species composition according to intertidal elevation were detected, with Pyropia orbicularis being more abundant in the low and mid intertidal zones and Porphyra mumfordii and Porphyra sp
As hypothesized for other cryptic species, we propose that niche partitioning could allow for the stable long-term coexistence of morphologically similar co-occurring species of bladed Bangiales
Our study provides useful insights into the mechanistic understanding of the growing diversity of cryptic species

Summary

Introduction

Cryptic species have been classically defined as genetically distinct taxa that have been erroneously classified under a single nominal species name because they are, at least superficially, morphologically indistinguishable [7,8]. These cryptic taxa have been shown to be especially common in the marine realm [9]. Cryptic species that are morphologically similar have been assumed to be ecologically similar, which implies that they require very similar resources [7,8]. If these species are coexisting, some niche differences would be expected [1,2,9,10,11]

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Conclusion