A comparison of habitat use, morphology, clinging performance and escape behaviour among two divergent green anole lizard (Anolis carolinensis) populations

We measured available and actual habitat use, morphology, escape behaviour and clinging ability in a large sample ( N  = 242) of green anoles, Anolis carolinensis , in a habitat consisting primarily of segregated dense clumps of broad leaves, Aspidistra elatior (Tulane University campus, LA) to compare against similar data collected previously from a more typical habitat c. 30 km away, consisting of continuous strands of bushes and trees (Good Hope Field, St. Charles Parish, LA). At Tulane the anoles perched primarily on the broad, smooth leaves of broad leaves, whereas in Good Hope Field (GHF) they predominantly perched on branches and tree trunks. The two populations differed significantly in morphology. In Tulane, the anoles tended to have shorter distal hindlimb elements, longer forelimb elements, and were more 'slender' than those at GHF. A comparison of escape behaviour showed population and sex differences. In both populations, females had significantly longer approach distances (i.e. were more 'wary') than males. These distances were, in addition, significantly longer at GHF than at Tulane for both sexes; this may be due to the potentially higher diversity and abundance of predators at GHF, although habituation to humans may also play a role. Anoles at Tulane had significantly larger toepads and higher clinging abilities than those at GHF. The enhanced clinging abilities of anoles at Tulane may have arisen due to their propensity to use smooth leaves as their primary substrate. Overall, our data reveal substantial ecological, behavioural, morphological, and functional differences among populations, some of which may be adaptive.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 223–234.     

Scale‐dependent processes of community assemblyin an African rift lake

1. Ecologists continue to debate whether the assembly of communities of species is more strongly influenced by dispersal limitations or niche‐based factors. Analytical approaches that account for both mechanisms can help to resolve controls of community assembly. 2. We compared littoral snail assemblages in Lake Tanganyika at three different spatial scales (5–25 m, 0.5–10 km and 0.5–27 km) to test whether spatial distance or environmental differences are better predictors of community similarity. 3. At the finest scale (5–25 m), snail assemblages shifted strongly with depth but not across similar lateral distances, indicating a stronger response to environmental gradients than dispersal opportunities. 4. At the two larger scales (0.5–27 km), both environmental similarity and shoreline distance between sites predicted assemblage similarity across sites. Additionally, canonical correspondence analysis revealed that snail abundances were significantly correlated with algal carbon‐to‐nitrogen ratio and wave energy. 5. Our results indicate that the factors governing assemblage structure are scale dependent; niche‐based mechanisms act across all spatial scales, whereas community similarity declines with distance only at larger spatial separations.     

Tetranucleotide microsatellites from the loggerhead sea turtle (Caretta caretta)

We describe primers and polymerase chain reaction conditions to amplify 15 tetranucleotide microsatellite loci from the loggerhead sea turtle (Caretta caretta). The primers were tested on 30 individuals that nested along the Georgia, USA coast. The primer pairs developed in this study yielded an average of 13.9 alleles per locus (range of 10–21), an average observed heterozygosity of 0.91 (range 0.79–1.00), and an average polymorphic information content of 0.88 (range 0.84–0.92).     

Dissecting the evolutionary impacts of plant invasions: bugs and beetles as native guides

The introduction of plants into new biogeographical realms is a main repercussion of human trade. The responses of native insects to alien plants may provide insight into how invaders influence ecological processes in their new communities. We illustrate this point with results from our field and lab studies of seed-feeding insects on alien plants. Soapberry bugs ( Jadera , Leptocoris ) have colonized several species of weedy invasive plants (sapindaceous trees and vines) in the United States and Australia. After initial reduction in physiological performance, they evolved behavioral, morphological, physiological and life history adaptations permitting more efficient exploitation of those hosts. Those changes occurred quickly, in fewer than 100 generations (ca. 30–50 years). The underlying genetic changes are surprisingly complex, and also involve loss of function on native hosts. Contrasting with this is the bruchine beetle ( Stator limbatus ) on seeds of leguminous trees. Large numbers of S. limbatus oviposit on an alien tree in Arizona, but few offspring survive. The main influence on larval survival is a maternal effect determined by the host the mother experiences as her eggs mature. Adaptive plasticity in egg size and composition may ultimately permit successful exploitation of novel resources. Together, these studies show that both complex genetic and developmental factors influence the integration of ecological and evolutionary processes in environments altered by anthropogenically initiated plant invasions. Tractable insect study systems may be valuable guides to understanding biotic dynamics in a changing world.     

Sex‐specific differences in spatial behaviour in the flesh fly Sarcophaga crassipalpis

Abstract Territoriality in the flesh fly Sarcophaga crassipalpis (Diptera: Sarcophagidae) is studied in the laboratory. In rectangular enclosures, male flies exhibit a lower tolerance (occupation of the same physical space) of same‐sex conspecifics than do females. In circular arenas, male flies show significantly higher levels of spatial separation among themselves (as determined from nearest neighbour analyses) than do females: males show a slight tendency towards a uniform distribution, whereas females exhibit a slight tendency towards clustering. The male spatial behaviour occurs during the photophase but not the scotophase, suggesting that visual cues are required for maintenance of inter‐individual spacing. No significant differences in male spacing behaviour occur between subjective day and subjective night in either constant dark or constant light conditions, suggesting that spatial patterning is not driven by a circadian rhythm.     

Beetles, parasitoids and tropical morning glories: a study in host discrimination

Abstract. 1. The common cassidid beetle, Stolas sp., feeds as both larva and adult on the leaves of the vine, Ipomoea asarifolia , a wild relative of the sweet potato.
2. In the region around Manaus (Amazonas State, Brazil) an average of 86% of the egg clutches were completely parasitized by the eulophid, Emersonella niveipes.
3. The wasp is phoretic on female beetles. In comparison with field beetles that lacked phoretic wasps, beetles associated with wasps produced eggs sooner, laid more egg clutches, and had a shorter laboratory life expectancy.
4. Host discrimination by the wasp is probably an active process rather than a passive association with randomly encountered beetles.
5. Emersonella niveipes also attacks Chelymorpha cassidea , a pest of sweet potato. Adults of Stolas sp. do not feed on sweet potato foliage nor occur in sweet potato fields, so they could provide a useful innocuous alternate host for Emersonella niveipes.
6. As some species in the Convovulaceae are important weeds in field crops, foliage-feeding cassidid beetles may play a useful role in weed suppression. Any biological control programme for the suppression of sweet potato pests may favour the spread of those noxious weeds that share the herbivore fauna of sweet potatoes.     

An independent method of deriving the carbon dioxide fertilization effect in dry conditions using historical yield data from wet and dry years

Accurate estimates of the fertilization effect that elevated carbon dioxide [CO₂] has on crop yields are valuable for estimation of future crop production, yet there is still some controversy over these estimates due to possible CO₂‐by‐water‐status interactions in chamber studies and the difficulty of conducting field experiments with elevated [CO₂]. This study presents a new method to estimate the CO₂ fertilization effect (CFE) in dry conditions (CFE_dry), based on a combination of historical yield and climatic data and field experiments that do not require elevated [CO₂]. It was estimated that approximately 50 years of increasing [CO₂] (i.e., a 73 ppm increase) resulted in a 9% and 14% improvement of yield in dry conditions for maize and soybean, respectively, which are similar to estimates derived from free air CO₂ enrichment (FACE) studies. The main source of uncertainty in this approach relates to differential effects of technology trends such as new cultivars in wet vs. dry years. Estimates of this technology–water interaction can be refined by further experimentation under ambient [CO₂], offering a cost‐effective path for improving CFE estimates. The results should prove useful for modeling future yield impacts of climate change, and the approach could be used to derive estimates for other species using relatively simple yield trials.     

Temperature effects on forest herbs assessed by warming and transplant experiments along a latitudinal gradient

Slow‐colonizing forest understorey plants are probably not able to rapidly adjust their distribution range following large‐scale climate change. Therefore, the acclimation potential to climate change within their actual occupied habitats will likely be key for their short‐ and long‐term persistence. We combined transplant experiments along a latitudinal gradient with open‐top chambers to assess the effects of temperature on phenology, growth and reproductive performance of multiple populations of slow‐colonizing understorey plants, using the spring flowering geophytic forb Anemone nemorosa and the early summer flowering grass Milium effusum as study species. In both species, emergence time and start of flowering clearly advanced with increasing temperatures. Vegetative growth (plant height, aboveground biomass) and reproductive success (seed mass, seed germination and germinable seed output) of A. nemorosa benefited from higher temperatures. Climate warming may thus increase future competitive ability and colonization rates of this species. Apart from the effects on phenology, growth and reproductive performance of M. effusum generally decreased when transplanted southwards (e.g., plant size and number of individuals decreased towards the south) and was probably more limited by light availability in the south. Specific leaf area of both species increased when transplanted southwards, but decreased with open‐top chamber installation in A. nemorosa. In general, individuals of both species transplanted at the home site performed best, suggesting local adaptation. We conclude that contrasting understorey plants may display divergent plasticity in response to changing temperatures which may alter future understorey community dynamics.