Environmental variation in a fossil scleractinian coral

Sample populations of Solenastrea fairbanksi , collected from different environments in the Pliocene Imperial Formation, can be distinguished by measurements of linear dimensions of the coenosteum and thickness of septal structures. In these characters, magnitudes of intercolony variance components are lower than interpopulation or intracolony components, suggesting that the variation is largely caused by environmental factors. Three patterns of mean variation exist between populations: (1) Highest means occur in shallow, offshore (high energy) environments. (2) Highest means occur in shallow environments with low turbidity (high light intensity). (3) Highest means occur in clear, deeper offshore environments (favorable nutrient supply). The distance between adjacent corallites and the inverse of coenosteal porosity follow the first pattern, measures of thickness of vertical corallite structures follow the second, whereas estimates of annual growth rate follow the third. Corallite diameters and columella thicknesses do not vary between populations. Comparisons with modern species show that many characters in S. fairbanksi respond to environmental factors in a manner different from similar characters in other scleractinian species. In fact, some inflexible characters in S. fairbunksi are highly flexible in other species.     

Suppression of Aedes aegypti by predatory Toxorhynchites moctezuma in an island habitat

Larval populations of the mosquito Aedes aegypti were suppressed by predatory Toxorhynchites moctezuma mosquito larvae released systematically in a village on Union Island (Saint Vincent and the Grenadines) during March-December 1988. Eggs and larvae of Tx.moctezuma were transported from Trinidad and introduced into all semi-permanent and permanent water-holding containers in the experimental village at Clifton. The semi-isolated village of Ashton served as control. Base-line Ae.aegypti indices (house, ovitrap, Breteau, cistern/tank, drum/barrel, small containers) were obtained for the two villages over a 4-month period prior to the introduction of the predatory Tx.moctezuma mosquito larvae. After sustained releases of predators for 5 months, all indices of Ae.aegypti were lower in the treated village than in the untreated village during the last 3 months of the year.     

Developmental plasticity in a meristic character: the number of tentacles in the lophophore of a bryozoan species

There is increasing interest among evolutionary biologists in developmental plasticity. Previously ignored by many as being irrelevant to evolution because a plastic response to an environmental change is not inherited, the current, more positive, view of plasticity focuses on the fact that, although any individual plastic response is nonheritable, the overall pattern of developmental response to environmental variation (i.e. the developmental reaction norm) is heritable and may vary among genotypes within a population. Characters subject to plastic variation, like those that are entirely genetically determined, may vary in continuous, meristic or discrete ways. Of these, the least work has been carried out on meristic variation. In the present study, we contribute to the rectification of this imbalance by examining the plastic response of the number of tentacles in the lophophore of a species of bryozoan, Membranipora membranacea, to three environmental variables: temperature, salinity and food concentration. Because the approach taken was an experimental one, unlike the majority of studies of bryozoan tentacles to date, we are able to make statements about the causality of variation in tentacle number. The main conclusions of the present study are: (1) that plastic responses occur to all three environmental variables; (2) that these are part of a more generalized plastic response in the overall development of the zooids rather than being lophophore‐specific; and (3) that the issue of whether the relevant developmental reaction norms are adaptive or not is an open (and interesting) question. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 541–551.