03173nas a2200397   4500008004100000245009200041210006900133300001200202490000700214520184500221653001302066653001202079653001502091653001502106653004402121653001602165653001202181653003702193653004102230653004702271653002802318653002202346653002902368653006402397653001702461653001802478653003202496653002502528653002802553653002802581653001502609653005802624653002902682100001802711856004602729       1996                        eng d00aSpecies boundaries, specialization, and the radiation of sponge-dwelling alpheid shrimp0 aSpecies boundaries specialization and the radiation of spongedwe  a307-3240 v583 aMicroevolutionary studies and natural history suggest that host-specialization has promoted the high diversity of tropical sponge-dwelling snapping shrimps (Decapoda, Alpheidae, Synalpheus). Yet the taxonomic difficulty of this genus has precluded rigorous tests of this hypothesis. S. rathbunae Coutiere is among the most abundant invertebrates inhabiting the framework of sponges and dead coral that forms the floor of Caribbean coral reefs. Even within a small area S. rathbunae exhibits the apparently wide variation in size, color, and morphology that has long frustrated efforts to identify and define species boundaries within this large ( gt 100 described species) genus. Here I show that sympatric populations of this nominal species occupying different sponge hosts display clear, concordant differences in allozyme genotypes and in multivariate morphometrics, confirming that the populations represent three distinct biological species. Moreover, careful field sampling revealed that the three S. rathbunae taxa and the closely related S. filidigitus Armstrong showed almost no overlap in the species of hosts occupied. Interestingly, while there was significant differentiation between Belizean and Panamanian populations of th eone taxon that occurred at both sites ( apprx 1500 km apart), these populations were recognizable as conspecific using both genetic and morphological characters. These results show that (1) diversity of higher than currently recognized, and (2) species of sponge-dwelling Synalpheus are highly host-specific, with related species distinctly segregated among hosts. Together with previous evidence of host race differentiation within shrimp species, these results suggest a primary role for resource specialization in the origin and/or maintenance of this group’s characteristically high diversity.10aAnimalia10aanimals10aArthropoda10aArthropods10aComparative and Experimental Morphology10aCrustaceans10aEcology10aEcology (Environmental Sciences)10aEnvironmental Biology/Animal [07508]10aEnvironmental Biology/Oceanography [07512]10aEnvironmental Sciences)10aEvolution [01500]10aEvolution and Adaptation10aGeneral and Systematic Zoology/Arthropoda-Crustacea [63554]10aInvertebrata10aInvertebrates10aMalacostraca (Malacostraca)10aMalacostraca [75112]10aMalacostraca: Crustacea10aMarine Ecology (Ecology10aPhysiology10aPhysiology and Pathology/Arthropoda-Crustacea [64054]10aSystematics and Taxonomy1 aDuffy, J., E.  uhttps://alpheidae.myspecies.info/node/17202080nas a2200145   4500008004100000245011600041210006900157260000800226300001200234490000700246520161600253100001301869700001801882856003401900       2008                        eng d00aInfluence of sociality on allometric growth and morphological differentiation in sponge-dwelling alpheid shrimp0 aInfluence of sociality on allometric growth and morphological di  cJul  a527-5400 v943 aEusocial societies are defined by a reproductive division of labour between breeders and nonbreeders that is often accompanied by morphological differentiation. Some eusocial taxa are further characterized by a subdivision of tasks among nonbreeders, often resulting in morphological differentiation among different groups (subcastes) that specialize on different sets of tasks. We investigated the possibility of morphological castes in eusocial shrimp colonies (Zuzalpheus, formerly part of Synalpheus) by comparing growth allometry and body proportions of three eusocial shrimp species with three pair-forming species (species where reproductive females and males occur in equal sex ratios). Allometry of eusocial species differed in several respects from that of pair-forming species in both lineages. First, allometry of fighting claw size among individuals other than female breeders was steeper in eusocial than in pair-forming species. Second, breeding females in eusocial colonies had proportionally smaller weapons (fighting claws) than females in pair-forming species. Finally, claw allometry changed with increasing colony size in eusocial species; large colonies showed a diphasic allometry of fighting claw and finger size, indicating a distinctive group of large individuals possessing relatively larger weapons than other colony members. Shrimp are thus similar to other eusocial animals in the morphological differentiation between breeders and nonbreeders, and in the indication that some larger nonbreeders might contribute more to defence than others. (C) 2008 The Linnean Society of London.1 aToth, E.1 aDuffy, J., E.  u<Go to ISI>://000256840900008