Nicole T. Rivera


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Institute of Evolution, Behaviour & Genetics
Biology I

University of Regensburg
D-93040 Regensburg
Germany

Phone : +49 941 943 2259
Fax : +49 941 943 3304

Nicole.Rivera(at)biologie.uni-regensburg.de

Curriculum vitae img07
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Analysing the origin of the biodiversity of land-dwelling crabs on the Greater Antilles


Mittermeier et al. (2004) had classified the Greater Antilles as one of the biodiversity hotspots of our planet. This archipelago is comprised of the islands Cuba, Hispaniola (consisting of the Dominican Republic and Haiti), Puerto Rico and Jamaica, which partly separate the West Atlantic from the Caribbean Sea by forming an island arc. It surely is no coincidence, that these relatively large and geological old islands exhibit an extraordinary high biodiversity. Biodiversity is the variation of taxonomic life forms within a given ecosystem. Islands, like the Greater Antilles are very isolated ecosystems. The size of the island, distance from the main land, and period of isolation determine the degree of evolutionary divergence. The isolation often results in high levels of adaptive radiations among the colonizing populations that came upon several unoccupied habitats – often very different from their own (Carson & Templeton 1984; Templeton 1980), in turn leading to high endemism. This is why so often many species are unique to these islands or regions.   img3

To investigate the biodiversity of the Greater Antilles, I use land-dwelling crabs as model organisms. Unlike their marine and semi-terrestrial relatives, they are characterized by not having to return to the sea for wetting their gills or for reproduction and spawn. Hence they are independent from the sea but not from freshwater. These, as land-dwelling denoted animals are characterized by their remarkably different variety of appearances on the different Caribbean islands. While you will only find one (Puerto Rico) to four (Cuba) different described species on the bigger islands of the Greater Antilles (Cuba, Hispaniola and Puerto Rico), which all appear in or next to streaming water, Jamaica holds at least ten different endemic freshwater crab species, which are very different in their body shape as well as in their habitat preferences. These Jamaican freshwater crabs (Diesel & Schubart, 2000; Schubart & Koller, 2005), with the same marine origin have also gone through an adaptive radiation in the past when colonizing the island. In these cases, not only the typical niche of streaming water was occupied (Sesarma bidentatum ecotype), also caves (Sesarma verleyi), humid rock rubble (Sesarma cookei), water-filled snail shells (Sesarma jarvisi) and water-filled leaf axels of bromeliads (Metopaulias depressus) were successfully colonized. One of my studied species, Metopaulias depressus, the bromeliad-crab additionally shows a remarkable social behaviour with brood-care and a helper-system by older siblings in order to enhance the survival of its offspring – a, for crabs, rather unusual behaviour (Diesel & Schubart, 2007).
In contrast to this biodiversity, the other three islands of the Greater Antilles seem to have a lack of species richness when it comes to freshwater crabs. Therefore, the topic of my PhD is, first of all, to investigate whether the lack of species richness on Hispaniola, Puerto Rico and Cuba is real or just a consequence of non-identification and non-characterization of cryptic species (see below). Secondly, comparing population-genetics of the diversity and differentiation among species should emphasize whether different strategies in dispersal or ecological adaptation could be the reason for the much higher diversity on Jamaica, or not.



Studied Species


Metopaulias depressus, Rathbun 1896 (Jamaica)

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Figure 1 A: Metopaulias depressus on Bromeliad; B: Juveniles feeding on a piece of centipede, the mother crab had caught; C: Shadow of M. depressus on Bromeliad; D: Mother crab with juveniles; E: M. depressus; F: empty snail shells brought into the bromeliad by M. depressus in order to increase pH-level of Water and to increase Ca2+-level. Pictures by Rudolf Diesel.



Epilobocera haytensis, Rathbun 1893 (Hispaniola)

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Figure 2 Epilobocera haytensis from Hispaniola. Picture by C. D. Schubart.


Epilobocera sinuatifrons, Rathbun 1866 (Puerto Rico)

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Figure 3 A: Epilobocera sinuatifrons in a cave in Puerto Rico; B: E. sinuatifrons:
left: Juvenile after hatching; right: Juvenile after one moult; C: E. sinuatifrons;
Pictures by Nicole T. Rivera.