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.

One potential consequence of sexual size dimorphism is conflict among characters. For example, a structure evolved for reproduction can impair performance during other activities (e.g., locomotion). Here we provide quantitative evidence for an animal overcoming an evolutionary conflict generated by differential scaling and sexual size dimorphism by obligatorily removing an undamaged reproductive organ, and thus dramatically enhancing its locomotor performance. The spider genus Tidarren (Araneae, Theridiidae) is interesting because, within several species presenting extreme sexual size dimorphism (males representing Ϸ1% of the total mass of the female), males voluntarily remove one of their two disproportionately large pedipalps (modified copulatory organs; a single one represents Ϸ10% of the body mass in an adult) before achieving sexual maturity. Whether the left or right pedipalp is removed appears to be random. Previous researchers have hypothesized that pedipalp removal might enhance locomotor performance, a prediction that has remained untested. We found that, for male Tidarren sisyphoides, maximum speed increased (44%) significantly and endurance increased (63%) significantly after pedipalp removal. Furthermore, spiders with one pedipalp moved Ϸ300% greater distances before exhaustion and had a higher survival after exertion than those with two pedipalps. Removal of the pedipalp may have evolved in male Tidarren because of enhanced abilities to search for females (higher endurance and survival after exertion) and to out-compete rival males on the female's web (higher maximum speed). Our data also highlight how the evolution of conflicts can result in the evolution of a novel behavior.A central tenet of optimality theory is that natural selection will optimize structure and performance resulting in an overall highly fit organism (1, 2). Many studies, however, have shown that the evolution of high performance in one task can lead to decreased performance during another task (e.g., refs. 3-5). In extreme cases of such apparent conflicts, a structure evolved for one activity can substantially impair performance during another activity. For example, Darwin (6) described how sexual selection for sex differences might lead to such functional conflicts, particularly in males. He depicted how the relatively elaborate feathers in some male birds result in enhanced reproductive success via female mate choice, yet also reduces or constrains flight capacities, thus potentially making the animal more susceptible to predators (7). A relatively unexplored area is how organisms cope with these constraints imposed by factors such as sexual selection, natural selection, or allometry. One view of constraints is that they limit or hinder morphological or behavioral change, but another possibility is that constraints can result in a novel phenotype or behavior (8, 9). For example, as plethodontid salamanders undergo evolutionary miniaturization (become smaller), they shift from a terrestrial to an arboreal lifestyle (10). This ...

A key assumption in ecomorphological studies is that morphology–function relationships are invariant due to underlying biomechanical principles. We tested the hypothesis that morphology–performance relationships are invariant across different seasons by examining how a key performance trait, bite force, and two aspects of morphology (head shape and dewlap size) changed seasonally in the field and in the laboratory in the green anole lizard Anolis carolinensis. We found that not only did bite force change seasonally (up to 80% within the same individual), but relationships between morphology and bite force are highly plastic. Of the three traits examined (bite force, head shape, and dewlap area), only head shape did not change seasonally. We noted opposing trends for how bite force and dewlap area changed seasonally; whereas dewlap areas were large in the spring, and small in the winter, bite forces were low in the spring and high in the winter. This pattern occurred because of a tradeoff at the individual level: individuals in the spring with large dewlaps and high bite forces diminish their dewlaps (but not bite force), whereas individuals with small dewlaps and low bite forces in the spring increase their bite forces (but not dewlap size). We also show that this trend was apparent both in the field (comparing different individuals) and the laboratory (comparing the same set of individuals under standardized conditions). Finally, seasonal changes were not consistent among individuals for either bite force or dewlap area, as individuals changed seasonally in proportion to their initial state. These findings cast doubt on the widely held view of invariant morphology–performance relationships, and offer a cautionary note for eco‐morphological studies.

The extent of genetic variation and levels of temporal and spatial heterogeneity was investigated, at six polymorphic protein-coding loci, in wild Atlantic salmon Salmo salar populations from six rivers of Asturias (Northern Spain). Also, stocks from northern Europe that were among those introduced to repopulate Asturian Rivers, and other wild Spanish and European populations were characterized. The lack of temporal variation observed suggests that effective population sizes of Asturian populations are sufficiently large to prevent extreme levels of genetic drift and that the introduced fish had a negligible contribution to the fisheries of Asturian rivers. # 2005 The Fisheries Society of the British Isles

Abstract.•Sexual size dimorphism (SSD) can strongly influence the evolution of reproductive strategies and life history. If SSD is extreme, and other characters (e.g., genitalic size) also increase with size, then functional conflicts may arise between the sexes. Spiders offer an excellent opportunity to investigate this issue because of their wide range of SSD. By using modern phylogenetic methods with 16 species of orb-weaving spiders, we provide strong evidence for the "positive genitalic divergence" model, implying that sexual genitalic dimorphism (SGD) increases as SSD increases. This pattern is supported by an evolutionary mismatch between the absolute sizes of male and female genitalia across species. Indeed, our findings reveal a dramatic reversal from male genitalia that are up to 87X larger than female genitalia in size-monomorphic species to female genitalia that are up to 2.8 X larger in extremely size-dimorphic species. We infer that divergence in SGD could limit SSD both in spiders, and potentially in other taxa as well. Further, male and female body size, as well as male and female genitalia size, are decoupled evolutionarily. Finally, we show a negative scaling (hypoallometry) of male and female genitalic morphology within sexes. Evolutionary forces specific to each sex, such as larger female size (increased fecundity) or smaller male size (enhanced mate-searching ability), may be balanced by stabilizing selection on relative genitalic size.