New species in old clades: Caribbean radiation of large orbweaving Eriophora spiders (Araneidae)

Abstract

The Caribbean region stands as a major diversity hotspot harboring a wealth of known diversity and yet shielding numerous understudied organisms. Taxonomic studies have been deficient in many megadiverse groups characterized by unclear taxonomic boundaries. Among these understudied organisms are the orb weaving spiders of the likely Neotropical genus Eriophora. Despite being large and charismatic spiders making conspicuous orbs, the genus currently consists of only seven species, of which three are dubiously placed and one insufficiently described. The three clearly valid Eriophora were described in the 19th century, with a lag of over 160 years since the last species discovery (E. edax (Blackwall, 1863)). Among Eriophora species, some are currently ´widespread´ and while similar in general habitus, exhibit varied color patterns among islands, and subtle genitalic variation, challenging morphological taxonomy. Eriophora taxonomy is characterized by instability with many species having been misplaced in the genus, or poorly described and subsequently placed as nomina dubia. Notably, Eriophora ravilla, a relatively common, widespread, and conspicuous species, has had a tumultuous taxonomic history. Initially described from Mexico, Herbert W. Levi subsumed in this species various other Neotropical taxa that while morphologically diverse, he considered to represent a continuum of intraspecific diversity. Here we present the first molecular analysis of Eriophora, focusing on the distribution and diversity of E. ravilla in the Caribbean. We find evidence for a much greater diversity of Eriophora species in the Caribbean than hitherto appreciated, and describe and diagnose four new species with in the ‘ravilla-clade´ based on molecular and morphological evidence: E. gudbjorgensis, E heimiri, E. mariusi, E. colettensis. These newly described species display morphological and genetic variation that matches their regional distribution: they are all single island Caribbean endemics. The identification of multiple short-range endemics derived from a formerly widespread species highlights the importance of integrated taxonomy in biodiversity discovery and conservation biology. This paper highlights the need to revisit the phylogeny and taxonomy of many lineages whose taxonomy stems in its entirety from pre-molecular revisions.