Intraspecific variation in carapace morphology among fiddler crabs (Genus Uca) from the Atlantic coast of Brazil

Kr Hampton,Cl Thurman,Jc Mcnamara,Mj Hopkins

doi:10.3354/ab00545

Abstract

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 20:53-67 (2014) - DOI: https://doi.org/10.3354/ab00545 Intraspecific variation in carapace morphology among fiddler crabs (Genus Uca) from the Atlantic coast of Brazil Kelsey R. Hampton1, Melanie J. Hopkins2, John C. McNamara3, Carl L. Thurman1,* 1Department of Biology, University of Northern Iowa, Cedar Falls, Iowa 50614-0421, USA 2GeoZentrum Nordbayern, Universität Erlangen-Nürnberg, Loewenichstraße 28, 91054 Erlangen, Germany 3Departamento de Biologia, FFCLRP, Universidade de São Paulo, Ribeirão Preto 14040-901, São Paulo, Brazil *Corresponding author: thurman@uni.edu ABSTRACT: Isolation due to geographical barriers should promote genetic and morphological divergence among populations. Marine currents flowing in opposing directions along landmasses can constitute barriers that isolate populations dependent upon aquatic dispersal. The distribution of fiddler crabs (genus Uca) is regulated primarily by the oceanic transport of their planktonic larvae and by available adult habitat. Along the Brazilian coast of eastern South America, the flow of 2 major oceanic currents separates northern from southern Uca populations, which may promote intraspecific divergence in ‘trans-Brazilian’ species. Populations of 10 Uca species were sampled at 64 locations north and south of the Ponta do Calcanhar, Rio Grande do Norte, Brazil. Carapace shape was assessed using geometric morphometrics to analyze 12 surface landmarks in 1319 female crabs. Carapace shape differs significantly in each species. In morphospace, the carapace forms of the 10 species appear to separate into traditional subgeneric clusters. Within the 8 species exhibiting trans-Brazilian distributions, northern and southern populations show distinct carapace differences. Depending on species, either the hepatic or the branchial region is larger in northern populations. Since significant genetic variability among such populations has not been confirmed, divergence in carapace shape suggests significant ecological modulation of phenotype within each species. Apparently, environmental differences between northern and southern localities exert a greater impact on carapace morphology than impeded gene flow. The drivers underpinning diversification of carapace shape remain unknown, however. KEY WORDS: Brachyura · Fiddler crab · Uca · Structural variation · Landmark analysis · Isolation · Ecophenotypy Full text in pdf format Supplementary material PreviousNextCite this article as: Hampton KR, Hopkins MJ, McNamara JC, Thurman CL (2014) Intraspecific variation in carapace morphology among fiddler crabs (Genus Uca) from the Atlantic coast of Brazil. Aquat Biol 20:53-67. https://doi.org/10.3354/ab00545 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 20, No. 1. Online publication date: January 13, 2014 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2014 Inter-Research.

Highlights

The coast of Brazil constitutes a composite of 5 contiguous tropical and subtropical biomes, stretching from above the Amazon River in the north to the border with Uruguay in the south (Thurman et al 2013)
We examine the impact of the major oceanic currents along the eastern coast of South America on phenotypic variation in several species of fiddler crabs from Brazil
The 10 Brazilian species are divided among 4 subgenera (Melo 1996): (1) subgenus Uca (U. maracoani (Latreille, 1802−1803)); (2) subgenus Boboruca (U. thayeri Rathburn, 1900); (3) subgenus Leptuca (U. cumulanta Crane, 1943, U. leptodactyla Rathbun, 1898, and U. uruguayensis Nobili, 1901); and (4) subgenus Minuca (U. burgersi Holthuis, 1967, U. mordax (Smith, 1870), U. rapax (Smith, 1870), U. victoriana von Hagen, 1987, and U. vocator (Herbst, 1804))

Summary

INTRODUCTION

The coast of Brazil constitutes a composite of 5 contiguous tropical and subtropical biomes, stretching from above the Amazon River in the north to the border with Uruguay in the south (Thurman et al 2013) Two of these biomes occur along the northern coast, and 3 along the southern coast, where they are separated by the Ponta do Calcanhar in Rio Grande do Norte state. The division of the major currents at the Ponta do Calcanhar, in particular, may significantly control gene exchange between the northern and southern populations of individual fiddler crab species. The 8 trans-Brazilian species exhibited morphological differences between their northern and southern populations, suggesting that the Ponta do Calcanhar might represent a biogeographical feature that underpins intraspecific divergence. Given available genetic information for Uca species from Brazil, such differentiation does not appear to correlate with underlying genetic structure (Wieman et al 2013)

MATERIALS AND METHODS

RESULTS

DISCUSSION