A new species of freshwater crab genus Fredius Pretzmann, 1967 (Crustacea: Brachyura: Pseudothelphusidae) from a naturally isolated orographic forest enclave within the semiarid Caatinga in Ceará, northeastern Brazil

A new species of freshwater crab, Fredius ibiapaba , is described and illustrated from a mid-altitude forested patch in Ipú (Ibiapaba plateau, Ceará, northeastern Brazil), between 635 to 782 m. The new species can be separated from its congeners by the morphology of its first gonopod: proximal half...

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Published inPeerJ (San Francisco, CA) Vol. 8; p. e9370
Main Authors Santos, Livanio C., Tavares, Marcos, Silva, José R.F., Cervini, Marcelo, Pinheiro, Allysson P., Santana, William
Format Journal Article
LanguageEnglish
Published San Diego PeerJ, Inc 29.06.2020
PeerJ Inc
Subjects
Amazon
Biodiversity
Brejos
Congeners
Fossils
Fredius
Freshwater Biology
Ibiapaba
Ipú
New species
Phylogenetics
Phylogeny
Refuges
River basins
rRNA 16S
Spines
Taxonomy
Zoology
Brazil
Roraima
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Summary:A new species of freshwater crab, Fredius ibiapaba , is described and illustrated from a mid-altitude forested patch in Ipú (Ibiapaba plateau, Ceará, northeastern Brazil), between 635 to 782 m. The new species can be separated from its congeners by the morphology of its first gonopod: proximal half remarkably swollen, sloping abruptly downwards distally to a nearly right-angular shoulder; mesial lobe much smaller than cephalic spine; cephalic lobe moderately developed; auxiliary lobe lip, delimiting field of apical spines, protruded all the way to distal margin of auxiliary lobe. Comparative 16S rDNA sequencing used to infer the phylogenetic placement of Fredius ibiapaba n. sp. revealed that it is the sister taxon of F. reflexifrons , a species which occurs allopatrically in the Amazon and Atlantic basin’s lowlands (<100 m). Fredius ibiapaba n. sp. and F. reflexifrons are highly dependent upon humidity and most probably were once part of an ancestral population living in a wide humid territory. Shrinking humid forests during several dry periods of the Tertiary and Quaternary likely have resulted in the fragmentation of the ancestral humid area and hence of the ancestral crab population. Fredius reflexifrons evolved and spread in a lowland, humid river basin (Amazon and Atlantic basins), whilst F. ibiapaba n. sp. evolved isolated on the top of a humid plateau. The two species are now separated by a vast intervening area occupied by the semiarid Caatinga
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ISSN:2167-8359
2167-8359
DOI:10.7717/peerj.9370