Showing papers in "Copeia in 1994"
TL;DR: In this article, the authors discuss the effects of stress on the human body, including muscle plasticity, muscle strength, and endocrine function, as well as the role of stress in these processes.
Abstract: Muscle Plasticity Grant B. McClelland and Graham R. Scott Cardiovascular System A. Kurt Gamperl and Holly A. Shiels Membranes and Metabolism James S. Ballantyne Oxygen Sensing Michael G. Jonz Intestinal Transport Martin Grosell Gill Ionic Transport, Acid-Base Regulation, and Nitrogen Excretion Pung-Pung Hwang and Li-Yih Lin Endocrine Disruption Heather J. Hamlin Thermal Stress Suzanne Currie and Patricia M. Schulte Physiology of Social Stress in Fishes Christina Sorensen, Ida Beitnes Johansen, and Oyvind Overli Pain Perception Victoria A. Braithwaite Chemoreception Warren W. Green and Barbara S. Zielinski Active Electroreception Signals, Sensing, and Behavior John E. Lewis Cardiac Regeneration Viravuth P. Yin Neuronal Regeneration Ruxandra F. Sirbulescu and Gunther K.H. Zupanc
1,400 citations
527 citations
TL;DR: Analysis of published and original data on the degree of sexual size dimorphism in snakes suggests that a previously documented correlation between SSD and geographic distribution is due to phylogenetic conservatism rather than to any functional relationship between the two variables.
Abstract: Published and original data on the degree of sexual size dimorphism (SSD) were collated for 374 species of snakes from eight families, to test for predicted associations between SSD and other aspects of reproductive biology. Data on the occurrence and form of male-male combat were also reviewed. Because phylogenetic conservatism was evident in most of the characteristics studied, the data were analyzed in two ways: (1) I looked for general patterns by treating each species as an independent unit; and (2) I superimposed the data onto a phylogenetic framework so that I could calculate independent contrasts within each lineage. Male-male combat has been reported in 124 species of snakes, and this combat takes many forms. For example, biting is common in nonvenomous species. Males grow larger, relative to conspecific females, in species with malemale combat than in species not recorded to show this behavior, and this association remains significant when analysis is restricted to independent phylogenetic contrasts. On a proximate level, the larger size of males in species with combat is due primarily to a prolongation of male growth after maturation. Fecundity advantages of larger body sizes in females may also influence SSD, because the degree of SSD correlates with the rate at which litter sizes increase with body size. The evolution of viviparity is associated with a consistent shift toward larger female size relative to male size. However, my analyses suggest that a previously documented correlation between SSD and geographic distribution is due to phylogenetic conservatism rather than to any functional relationship between the two variables.
428 citations
TL;DR: In a collection rich in implications for all fields of ecology, leading lizard ecologists demonstrate the utility of the phylogenetic approach in understanding the evolution of morphology, physiology, behavior, and life histories.
Abstract: In a collection rich in implications for all fields of ecology, leading lizard ecologists demonstrate the utility of the phylogenetic approach in understanding the evolution of morphology, physiology, behavior, and life histories. Lizards, which are valued for their amenability to field experiments, have been the subject of reciprocal transplant experiments and of manipulations of resource availability, habitat structure, population density, and entire sections of food webs. Such experiments are rapidly rebuilding ecological theories as they apply to all organisms. As a demonstration of state-of-the-art historical and experimental research and as a call for philosophical engagement, this volume will join its predecessors--Lizard Ecology: A Symposium (Missouri, 1967) and Lizard Ecology: Studies of a Model Organism (Harvard, 1983)--in directing ecological research for years to come.Lizard Ecology contains essays on reproductive ecology (Arthur E. Dunham, Lin Schwarzkopf, Peter H. Niewiarowski, Karen Overall, and Barry Sinervo), behavioral ecology (A. Stanley Rand, William E. Cooper, Jr., Em!lia P. Martins, Craig Guyer, and C. Michael Bull), evolutionary ecology (Raymond B. Huey, Jean Clobert et al., Donald B. Miles, and Theodore Garland, Jr.), and population and community ecology (Ted Case, Robin M. Andrews and S. Joseph Wright, Craig D. James, and Jonathan B. Losos).
272 citations
TL;DR: In this article, the authors studied correlations among traits related to body size and reproductive behavior in marine turtles, using data from 96 different populations representing seven species. And they found important differences among species in the way life-history traits correlated with one another.
Abstract: We studied correlations among traits related to body size and reproductive behavior in marine turtles, using data from 96 different populations representing seven species. Our analyses focused on patterns of phenotypic covariation among species and among populations within species. At the species level, body size correlated positively with several reproductive traits, including egg size and overall reproductive effort. A trade-off between clutch size and egg size was confirmed for marine turtles, after factoring out the effects of body size. Patterns of variation within species were different from those among species. For example, in five out of six species there was a positive relationship between adult body size and clutch size, although this correlation was not found at the interspecific level. We also found important differences among species in the way life-history traits correlated with one another. Four species having a sufficient number of samples exhibited congruent worldwide patterns of body size variation. A comparative approach may prove useful for extending demographic models developed for loggerhead turtles to less well-known species, even though many of the model parameters have not been estimated for other species.
211 citations
TL;DR: Path analysis indicated no one variable with great overall influence on antipredator behavior in these lizards but rather a combined influence of several environmental factors.
Abstract: Antipredator behavior was measured in four populations of zebra-tailed lizards (Callisaurus draconoides) and two populations of greater earless lizards (Cophosaurus texanus). Lizards were approached in the field, and five measures of wariness were recorded. Callisaurus had significantly greater approach distance and greater final distance than did Cophosaurus. Among populations of Callisaurus, lizards were wariest at the site with the least plant cover. Within populations, air temperature, the directness of the observer's approach, and the lizard's distance to nearest cover when first sighted had significant direct effects on flight behavior based on path analysis. Windiness and time of day had significant direct effects and indirect effects through their relationships with air temperature and distance to cover. Path analysis indicated no one variable with great overall influence on antipredator behavior in these lizards but rather a combined influence of several environmental factors.
168 citations
TL;DR: The result supports the hypothesis of natal homing in green turtles and the presence or absence of Florida haplotypes among other western Atlantic populations will provide a critical test of these alternate hypotheses.
Abstract: Mitochondrial DNA (mtDNA) sequences of the control region were obtained for the Costa Rica and Florida colonies of the green turtle (Chelonia mydas) to test the hypothesis that gravid females return to their natal beaches to lay their eggs. Analyses of intra- and intergroup variation of these sequences revealed that the two colonies are structured differentially along maternal lineages and that mtDNA diversity is unusually high in the Florida population. The former result supports the hypothesis of natal homing in green turtles. For the latter, two explanations are provided: (1) that the Florida colony is the product of admixture (immigration from multiple sources); or (2) that it is a remnant of a larger, ancestral population. The presence or absence of Florida haplotypes among other western Atlantic populations will provide a critical test of these alternate hypotheses.
129 citations
126 citations
TL;DR: Fifty mating events in free-living nurse sharks were observed over a nine-day period in the Dry Tortugas island cluster in the Florida Keys and showed the presence of free, nonpackaged sperm cells.
Abstract: Fifty mating events in free-living nurse sharks (Ginglymostoma cirratum) were observed over a nine-day period in the Dry Tortugas island cluster in the Florida Keys. Four stages of mating were identified: precoupling, coupling, positioning and alignment, and insertion and copulation. Copulation was observed and filmed in four of the mating events. Seminal fluid released into the water was obtained following one copulation and showed the presence of free, nonpackaged sperm cells. At least 10 of the events involved multiple males attempting copulation with single females.
125 citations
TL;DR: Observed changes in life-history traits with diet are assessed in relation to models which predict the optimal timing of metamorphosis in larval Pacific treefrogs.
Abstract: The quality of algae as food for larval Pacific treefrogs, Hyla regilla, varies among algal taxa. Tadpole diets were manipulated in enclosures in the South Fork Eel River, northern California. Enclosed tadpoles were fed ad libitum one of the dominant filamentous green algae (Cladophora, Zygnema, Mougeotia, or Oedogonium), the dominant cyanobacterium in the habitat (Nostoc), flocculent detritus, or a commercial reptile/amphibian food. Tadpoles in a control treatment were not fed but had access to seston which deposited in all enclosures. Diet treatment significantly affected weekly growth rates, as well as time to and weight at metamorphosis. Tadpoles grew most rapidly on filamentous green algae with diatom epiphytes and on the commercial food. Tadpoles fed epiphytized Cladophora metamorphosed 27.1% (11.7 days) sooner and weighed 38.9% (70 mg) more than tadpoles fed Cladophora cleaned of diatoms. In comparison to tadpoles fed Mougeotia, which does not support epiphytes, tadpoles fed epiphytized Cladophora metamorphosed 37.4% (19.7 days) sooner and weighed 31.6% (50 g) more. Tadpoles with the lowest growth rates were those filtering deposited seston or flocculent detritus. Observed changes in life-history traits with diet are assessed in relation to models which predict the optimal timing of metamorphosis.
TL;DR: Spikedace syntopic with red shiner displayed a niche shift into currents significantly swifter than those selected when in isolation, which suggests negative interspecific interactions potentially detrimental to the indigenous species.
Abstract: ern North America by the nonnative red shiner (Cyprinella lutrensis) seems linked with the dramatic decline of a threatened cyprinid (spikedace, Medafulgida) native to the Gila River subbasin. The mechanism by which red shiner impacts spikedace is unknown. Two hypotheses have been offered: displacement of the native through competitive interaction with invader, and replacement of native by nonnative as a result of environmental perturbation. To ascertain whether spikedace was being actively displaced by red shiner, we compared niche requirements of each in syntopy, allotopy, and disjunct allopatry. Fishes were collected by seining one to three sites in each of six different stream reaches; and current velocity, substrate particle size, and water depth were measured at each site. Red shiner occupied similar microhabitat whether allopatric, allotopic, or syntopic with spikedace. Spikedace occupied the same microhabitat when allopatric or allotopic to red shiner. However, spikedace syntopic with red shiner displayed a niche shift into currents significantly swifter than those selected when in isolation. Displacement of spikedace by red shiner suggests negative interspecific interactions potentially detrimental to the indigenous species.
TL;DR: In western North Carolina, adult wood frogs and American toads often occur syntopically but segregate with respect to breeding habitat, and their role in structuring aquatic communities via opportunistic predation may be more important than previously realized.
Abstract: In western North Carolina, adult wood frogs and American toads often occur syntopically but segregate with respect to breeding habitat. American toads arrive at breeding ponds 4-10 wk after wood frogs and typically select breeding sites that lack wood frog tadpoles. In an experiment conducted in seminatural ponds, adult toads completely avoided ovipositing in ponds with wood frog tadpoles. Additional experiments strongly suggest that predation of wood frog tadpoles on toad eggs and larvae is the primary reason for the evolution of adult avoidance behavior in toads. In one set of experiments, toad eggs and hatchlings suffered complete mortality within two days after being placed in artificial ponds containing natural densities of wood frog tadpoles. Similar mortality occurred when eggs and hatchlings were introduced into natural breeding sites. In one experiment in which 2000 toad hatchlings were added to natural ponds, all were killed and consumed within 45 min by wood frog tadpoles. Although tadpoles of most anurans are considered to be microphagous suspension feeders that occupy lower trophic levels of food chains, a growing body of evidence indicates that many tadpoles can temporarily shift feeding modes to become upper level, macrophagous predators. Because facultative predators such as wood frog tadpoles often reach far higher densities in ponds than do top predators, their role in structuring aquatic communities via opportunistic predation may be more important than previously realized.
TL;DR: It is speculated that overwintering in rodent burrows at the sand-alluvial interface of the study site to overwinter increases overwinters' survival because of decreased likelihood of exposure to freezing subsurface temperatures, greater structural stability of burrows, and lower risk of predation.
Abstract: winders traveled on average 60% of the days monitored during their activity season (April-Oct.), with a resultant mean daily distance traveled of 117.8 ? 11.2 m/day. Although direction of travel was generally random, sidewinders exhibited significant directionality during the fall as they moved eastwardly to the sand-alluvial interface of the study site to overwinter. I speculate that overwintering in rodent burrows at the sand-alluvial interface increases overwintering survival because of decreased likelihood of exposure to freezing subsurface temperatures, greater structural stability of burrows, and lower risk of predation. Activity ranges of C. cerastes, calculated by minimum convex polygon (F = 23.2 + 2.8 ha) and harmonic mean (9 = 20.9 ? 2.6 ha) methods, are among the largest documented for snakes. For this population of sidewinders, there were no significant differences in activity range size between sexes or age classes (subadult vs adult). Core areas of activity (harmonic mean 50% isopleths) averaged 9.2 + 0.9% of total activity range size (harmonic mean 95% isopleths) and also did not differ in size between sexes and age classes. Activity range size did not correlate with body size (SVL and mass), although it did correlate with the number of locality coordinates used in its calculation. Activity ranges of individual sidewinders overlapped extensively on the study site, and snakes commonly shifted their centers of activity seasonally. Sidewinders moved their activity centers during the fall to the site's sand-alluvial edge and returned to the site's sandy region following emergence from hibernation.
TL;DR: The dynamics of the young-of-the-year (YOY) fish community in a portion of the floodplain and adjacent channel of the Tallahatchie River, Mississippi, is studied by quantifying temporal and spatial variation in abundances of larval and juvenile fishes.
Abstract: We studied the dynamics of the young-of-the-year (YOY) fish community in a portion of the floodplain and adjacent channel of the Tallahatchie River, Mississippi, by quantifying temporal and spatial variation in abundances of larval and juvenile fishes. Multivariate comparisons of relative abundance data indicated that assemblage composition differed over time and among sampling locations. A spring assemblage consisting of larval gizzard shad (Dorosoma cepedianum), larval crappie (Pomoxis spp.), and larval darters (Etheostoma and Percina spp.) dominated samples from mid-April to early June. Composition of the spring assemblage did not differ among habitats although more larval fishes were caught in warmer, more lentic habitats. This assemblage was replaced in late June by a group consisting of larval and juvenile sunfishes (Lepomis spp.), YOY mosquitofish (Gambusia afinis), and juvenile shiners (Cyprinella and Notropis spp.). The relative abundance of fishes in this assemblage differed among habitats; larval and juvenile sunfish were most abundant in habitats exhibiting low flow rates and high temperatures, and juvenile shiners were most abundant in moderate to high flow habitats. High larval fish abundance in floodplains stems, in part, from the presence of larvae of species that inhabit both the channel and the floodplain as adults.
TL;DR: In this paper, the authors measured net water flux and tolerance to dehydration as a function of size at metamorphosis in the desert anuran Scaphiopus couchii (Anura: Pelobatidae).
Abstract: We measured net water flux and tolerance to dehydration as a function of size at metamorphosis in the desert anuran Scaphiopus couchii (Anura: Pelobatidae). Experimental conditions were based on extensive sampling in the field of environmental conditions available to and encountered by recently metamorphosed toadlets. Size had little effect on dehydration tolerance. Nevertheless, because larger toadlets lost water at a lower mass-specific rate, they had an advantage in the time available before reaching a critical level of dehydration. Field studies also provide a context for interpreting physiological differences in water loss. In the desert, moist soil has a patchy distribution in space and time. Larger metamorphs, because they can survive longer in the intervening dry areas, may have more time to locate suitable microhabitats.
TL;DR: The mbuna group is generally thought to be a monophyletic assemblage, but results suggest that it is actually paraphy letic, and in contrast to the high morphological diversity among Malawi haplochro mine species, mtDNA sequence divergence was found to be remarkably low.
Abstract: were distinguished, two of which were major clades, represented by a large number of species. The other four lineages were each represented by a single species with a divergent mtDNA haplotype. One of the two major clades was composed of the shallow-water, rock-dwelling mbuna species, whereas the other included a diverse array of sand-dwelling and pelagic species. A number of taxa, found to be firmly embedded within the mbuna clade, are quite distinct in mor phology and generally inhabit deeper, sediment-rich areas rather than the rocky habitats typical of other mbuna. The mbuna group is generally thought to be a monophyletic assemblage, but these results suggest that it is actually paraphy letic. In contrast to the high morphological diversity among Malawi haplochro mine species, mtDNA sequence divergence was found to be remarkably low. This finding underscores the unprecedented rapidity of speciation and evolutionary plasticity in this fish species flock. B eginning with the earliest collections and vented identification of sister-group relation descriptions of Malawi haplochromines, ships (though many autapomorphic traits are taxonomists have been challenged and frus present). Second, an abundance of parallelism trated by attempts to reconstruct the phyloge has made it difficult to assure that shared traits netic history of this fauna. Two primary obsta are actually synapomorphic (Eccles and Tre cles have confounded this reconstruction. First, wavas, 1989). Early work on the Malawi ich a paucity of shared derived traits often pre- thyofauna revealed a large number of new spe
TL;DR: High intrapopulation frequencies of pelvic reduction apparently have evolved repeatedly within Cook Inlet, but gene flow is probably important in spreading genetic variation for pelvic reduction among populations.
Abstract: Loss of one or more elements of the pelvic complex occurs at substantial frequencies (-5%) in 55 and at lower frequencies in 42 of 204 populations of Gasterosteus aculeatus sampled from freshwater sites around Cook Inlet, Alaska. Populations with substantial pelvic reduction are widely distributed and interspersed among those lacking it. Intrapopulation phenotype frequencies vary greatly within limited areas but may be similar in distant populations. Intrapopulation phenotype frequency distributions include bimodal, flat, normal, skewed, and truncated; and their form may vary among adjacent populations. High intrapopulation frequencies of pelvic reduction apparently have evolved repeatedly within Cook Inlet, but gene flow is probably important in spreading genetic variation for pelvic reduction among populations. Divergent populations of Cook Inlet threespine stickleback should be treated as parts of an endemic radiation, which warrants special consideration for conservation as a unit.
TL;DR: The large egg size of amphidromous fish promotes salinity tolerance of offspring, so lower salinity may have resulted in evolution of smaller eggs in land-locked populations.
Abstract: We examined the reproductive traits and early survival of ayu, Plecoglossus altivelis (Osmeridae), from amphidromous and land-locked populations under controlled rearing conditions to evaluate the adaptive significance of egg size variation. Spawning was earlier for land-locked than for amphidromous ayu and was earlier for larger individuals within a population. Amphidromous fish produced larger eggs than land-locked fish; and for both forms, smaller individuals produced larger eggs within a population. Water temperature declined through the spawning season, and both salinity and low water temperature markedly damaged small offspring from small eggs. The large egg size of amphidromous fish promotes salinity tolerance of offspring, so lower salinity may have resulted in evolution of smaller eggs in land-locked populations. Smaller individuals within a population had larger egg sizes, which may be an adaptive response to enhance offspring survival at low water temperatures under changing environments.
TL;DR: The degree to which absolute body size is correlated with other ecological variables in interspecific comparisons is examined and interspecific associations between ecological traits are investigated after the confounding effect of absolute body sizes is removed from the analysis.
Abstract: This paper summarizes published and original data on ecological characteristics of 103 species of Australian snakes, based on dissection of > 22,000 specimens in museum collections. Principal Component Analyses suggest that much of the interspecific variance in ecology is the result of differences in mean adult body sizes. Thus, I examine the degree to which absolute body size is correlated with other ecological variables in interspecific comparisons and investigate interspecific associations between ecological traits after the confounding effect of absolute body size is removed from the analysis. Mean adult body size is significantly correlated with measures of population structure (adult sex ratio), growth trajectories (size at maturation relative to mean adult size, and sexual size dimorphism), mating systems (presence or absence of male-male combat), reproductive biology (offspring size, clutch size, reproductive mode, and reproductive frequency in females), and food habits (proportional composition of major prey types). Phylogenetically based analyses show that some of these interspecific correlations are the result of phylogenetic conservatism, whereas others reflect underlying functional relationships. When these kinds of allometric effects are taken into account, clear patterns in interspecific variation in life-history attributes are revealed. For example, a trade-off is apparent between clutch size and offspring size: species with relatively large clutches produce relatively small offspring. Offspring size is unaffected by shifts in reproductive mode (oviparity/viviparity) but is correlated with the extent of postmaturational growth by females (in species with relatively large offspring, females delay maturation until they reach a large size). The presence or absence of male-male combat in a species affects adult sex ratio in collections (probably via sex biases in catchability), growth trajectories in males, and the degree of sexual size dimorphism.
TL;DR: There was considerable dietary overlap among three co-occurring salamander size classes suggesting that food resources were not strongly partitioned among them, and predation on benthic invertebrates by larval Dicamptodon tenebrosus is size selective.
Abstract: Pacific giant salamander larvae in a northern California stream were found to consume a wide variety and size range of prey in a one-year diet study. Aquatic insects made the greatest contribution to salamander diets, both numerically and by volume, with ephemeroptera nymphs being the most frequently consumed prey type. Although terrestrial invertebrates that fell into the stream constituted a small proportion of the diet numerically, they comprised a large proportion of diet volume throughout the year. Stomach contents mass and the proportion of intact prey in the stomach contents did not vary with time of day. In contrast, larval salamanders exhibited a strong diel activity pattern, being inactive and under cover during the day and active on the streambed surface at night. As larval salamanders grew, they included larger prey in their diet but continued to consume large numbers of very small prey. Small salamanders were able to consume a large proportion of the size range of most common prey, whereas only large salamanders were capable of consuming rare, large prey (e.g., large odonates, megalopterans, fish, and small salamanders). There was considerable dietary overlap among three co-occurring salamander size classes suggesting that food resources were not strongly partitioned among them. Relative abundances of prey in the diet were not correlated with their relative abundances in the environment, indicating that larval salamanders feed preferentially on certain prey taxa while avoiding, not encountering, or being unable to capture others. Electivity values were consistently positive for ephemeropterans and large, mobile invertebrate predators but were consistently negative for small, cryptic invertebrates and case-building caddisflies. In addition, mean sizes of three common mayflies were consistently larger in salamander stomach contents than in the benthos, indicating that predation on benthic invertebrates by larval Dicamptodon tenebrosus is size selective.
TL;DR: A population of the northern fence lizard was studied for four years along a riverine pine bluff in northern Mississippi for comparison with previous studies and to identify factors influencing mortality rates and annual variations in reproduction, growth, survival, and population densities.
Abstract: A population of the northern fence lizard Sceloporus undulatus was studied for four years along a riverine pine bluff in northern Mississippi for comparison with previous studies and to identify factors influencing mortality rates and annual variations in reproduction, growth, survival, and population densities. Reproductive parameters were similar to those of other eastern woodland populations, with clutch size averaging 9.4. Most males and females were reproductive by age one year. Age ratios were 1:1 between yearlings and older adults; sex ratios favored females more in older age groups and resulted from higher mortality rates in males. Annual survivorship averaged 30% for yearlings and adults and showed a loose inverse correlation with injury rates (broken tails) on different vegetational zones of the study area. Spring population densities were among the highest reported for this species, at up to 72 (717 g)/ha. Tree trunks (mostly pines) were perch sites >70% of the time. Females used larger diameter oak trees more than did males, possibly reducing injury rates and enhancing survivorship. Growth, volume of food in stomachs, reproduction, and survival seemed little affected by variations in precipitation between two years; rather, population fluctuations seemed most critically tied to survival from egg to hatchling. Two life tables were most similar to one for an Ohio population in survival to first breeding (5-12%), cohort generation time (1.8 yr), and age two contributing most to the net reproductive rate.
TL;DR: In comparison with other studies of racers in which data was collected, analyzed, and presented in the same manner as in this study, home range size and daily movement of South Carolina racers were significantly greater.
Abstract: Racers (Coluber constrictor) were monitored with radiotelemetry in an old field/forest habitat surrounding a Carolina bay in South Carolina. Racers were active on approximately 70% of days; inactive snakes usually were in ecdysis. Active racers were relocated on the ground surface (40%), above ground in shrubs and trees (35%), and underground (25%). Habitats in which racers were relocated were thickets and grassland shrubs (50%), woodland/forest (25%), and grassland (25%). Active snakes moved an average of 104 m/d within home ranges averaging 12.2 ha estimated as minimum convex polygons. The home range of each snake included at least a portion of the bay and overlapped with home ranges of other snakes. In comparison with other studies of racers in which data were collected, analyzed, and presented in the same manner as in this study, home range size and daily movement of South Carolina racers were significantly greater. Possible explanations for the greater movement include trophic level differences and a proximate response to a local drought.
TL;DR: The results suggest that color change may function both in predator avoidance and in thermoregulation or water balance, and further investigations of color change responses to differently hued backgrounds, of the magnitude and biological significance of color-induced changes in body temperature and rates of evaporative water loss, and ofcolor change in freeranging animals are needed.
Abstract: In an effort to better understand the function of physiological color change in anurans, we measured color change responses of the green treefrog, Hyla cinerea, to background brightness and temperature. We used our results to compare color and color change responses of males and females and to test two hypotheses for the function of physiological color change in anurans: (1) that color change serves to prevent detection by visual predators, and (2) that color change functions in thermoregulation or water balance. We found that (1) males are generally darker than females but the sexes exhibit similar color change responses, (2) treefrogs become lighter on brighter backgrounds, (3) treefrogs become lighter at higher temperatures, and (4) there is a background-by-temperature interaction such that color change responses to one variable depend on the level of the other. Our results suggest that color change may function both in predator avoidance and in thermoregulation or water balance. However, further investigations of color change responses to differently hued backgrounds, of the magnitude and biological significance of color-induced changes in body temperature and rates of evaporative water loss, and of color change in freeranging animals are needed.
TL;DR: The results suggest that female advertisement can influence the intensity of sexual selection because large males can restrict access of small males to contested females and female advertisement facilitates the ability of large males to focus their efforts where mating success is most likely to result in reproductive success.
Abstract: We examined the relative importance of visual and chemical cues in the advertisement of female receptivity in the sailfin molly and whether males of different body sizes respond differently to those cues. Experimental treatments that allowed only olfactory cues without any visual cue or direct contact elicited no responses from males. Receptivity was perceived through a chemical cue that's effectiveness required direct contact between male and female. However, males of different sizes reacted differently to this contact signal. Large males were less interested in nonreceptive females than in receptive ones, whereas small males did not differentiate between nonreceptive and receptive females. The results suggest that female advertisement can influence the intensity of sexual selection because large males can restrict access of small males to contested females and female advertisement facilitates the ability of large males to focus their efforts where mating success is most likely to result in reproductive success.