@article {314,
	title = {Resource-associated population subdivision in a symbiotic coral-reef shrimp},
	journal = {Evolution},
	volume = {50},
	number = {1},
	year = {1996},
	note = {Article.0014-3820English},
	pages = {360-373},
	abstract = {The importance of sympatric speciation remains controversial. An empirical observation frequently offered in its support is the occurrence of sister taxa living in sympatry but using different resources. To examine the possibility of sympatric differentiation in producing such cases, I measured genetic, behavioral, and demographic differentiation between populations of the tropical sponge-dwelling shrimp Synalpheus brooksi occupying two alternate host species on three reefs in Caribbean Panama. This species belongs to an apparently monophyletic group of gtoreq 30 species of mostly obligate, host-specific sponge-dwellers, many of which occur in sympatry. Demographic data demonstrated the potential for disruptive selection imposed by the two host species: shrimp demes from the sponge Agelas clathrodes were consistently denser, poorer in mature females, more heavily parasitized by branchial bopyrid isopods, and less parasitized by thoracic isopods, than conspecific shrimp from the sponge Spheciospongia vesparium. Laboratory assays demonstrated divergence in host preference: shrimp on all three reefs tended to choose their native sponge species more often than did conspecific shrimp from the other host. Because S. brooksi mates within the host, this habitat selection should foster assortative mating by host species. A hierarchical survey of protein-electrophoretic variation also supported host-mediated divergence, revealing the following: (1) shrimp from the two hosts are conspecific, as evidenced by absence of fixed allelic differences at any of nine allozyme loci scored; (2) strong genetic subdivision among populations of this philopatric shrimp on reefs separated by 1-3 km; and (3) significant host-associated genetic differentiation within two of the three reefs. Finally, intersexual aggression (a proxy for mating incompatibility) between shrimp from different host species was significantly elevated on the one reef where host-associated genetic differences were strongest, demonstrating concordance between genetic and behavioral estimates of divergence. Adjacent reefs appear to be semi-independent sites of host-associated differentiation, as evidenced by differences in the degree of host-associated behavioral and genetic differentiation, and in the specific loci involved, on different reefs. In philopatric organisms with highly subdivided populations, such as S. brooksi, resource-associated differentiation can occur independently in different populations, thus providing multiple "experiments" in differentiation and resulting in a mosaic pattern of polymorphism as reflected by neutral genetic markers. Several freshwater fishes, an amphipod, and a snail similarly show independent but remarkably convergent patterns of resource-associated divergence in different conspecific populations, often in the absence of obvious spatial barriers. In each case, substantial differentiation has occurred in the face of continuing gene flow.},
	keywords = {allozyme, amphipod [Malacostraca]},
	author = {Duffy, J. E.}
}
@article {344,
	title = {Multiple origins of eusociality among sponge-dwelling shrimps (Synalpheus)},
	journal = {Evolution},
	volume = {54},
	number = {2},
	year = {2000},
	note = {Article.0014-3820English},
	month = {April},
	pages = {503-516},
	abstract = {As the most extreme expression of apparent altruism in nature, eusociality has long posed a central paradox for behavioral and evolutionary ecology. Because eusociality has arisen rarely among animals, understanding the selective pressures important in early stages of its evolution remains elusive. Employing a historical approach to this problem, we used morphology and DNA sequences to reconstruct the phylogeny of 13 species of sponge-dwelling shrimps (Synalpheus) with colony organization ranging from asocial pair-bonding through eusociality. We then used phylogenetically independent contrasts to test whether sociality was associated with evidence of enhanced competitive ability, as suggested by hypotheses invoking an advantage of cooperation in crowded habitats. The molecular, morphological, and combined data each strongly supported three independent origins of monogynous, multigenerational (eusocial) colony organization within this genus. Phylogenetically independent contrasts confirmed that highly social taxa, with strong reproductive skew, have significantly higher relative abundance within the host sponge than do less social taxa, a result that was robust to uncertainty in tree topology and varying models of character change. A similar tendency for highly social species to share their sponge with fewer congener species was suggestive, but not significant. Because unoccupied habitat appears to be limiting for many sponge-dwelling shrimp species, these data are consistent with hypotheses that cooperative social groups enjoy a competitive advantage over less organized groups or individuals, where independent establishment is difficult, and that enemy pressure is of central importance in the evolution of animal sociality.},
	keywords = {[01500] Evolution, [07003] Behavioral biology - Animal behavior, [07502] Ecology: environmental biology - General and methods, [64054] Invertebrata:comparative, [75112] Malacostraca, altruism, Animalia, Arthropoda, Arthropods, asocial pair-bonding, Behavior, colony organization: monogynous, Crustacea, Crustaceans, dna, eusociality, Evolution and Adaptation, experimental morphology, Invertebrata, Invertebrates, Malacostraca: Animals, Morphology, multigenerational, multiple origins, phylogeny, physiology and pathology - Arthropoda: crustacea, social evolution, Synalpheus [Malacostraca]},
	url = {file://localhost/Users/kristinhultgren/Desktop/Papers/Duffy_Morrison_Rios_2000.pdf},
	author = {Duffy, J. E. and Morrison, C. L. and Rios, Ruben}
}
