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Introduction Patterns of reproduction are often governed by environmental factors, such as temperature, precipitation, or tidal cycles. For systems that span a wide latitudinal range, differences in these environmental factors [...], The timing of reproduction is often governed by environmental variables, such as temperature or rainfall. Understanding how environmental variables affect mating dynamics is necessary to predict how systems and populations may adapt to changing environmental conditions and is crucial for management of threatened species. The American horseshoe crab (Limulus polyphemus) ranges from the Yucatan to Maine in distinct populations that differ in their timing of reproduction; while most populations have only one breeding period during the spring, some southern populations have two breeding periods. Here we discuss seasonal patterns of reproduction in a Florida Gulf coast population where horseshoe crabs have two periods of breeding: one in the spring and another in the fall. We used environmental measurements, spawning surveys, mark-recapture, and measurements of adult traits and spawning behavior to compare reproductive parameters between the two spawning seasons over three years. We then evaluated whether environmental conditions affect fall and spring horseshoe crab nesting patterns similarly and whether fall and spring horseshoe crabs should be considered two separate populations. We found significant differences in environmental conditions across seasons and in a wide variety of horseshoe crab traits and nesting parameters. Furthermore, environmental conditions affected nesting behaviors of fall and spring horseshoe crabs differently. However, some individuals spawn during both seasons, suggesting that trait differences may be attributable to environmental effects during development or seasonal plasticity, rather than genetic differences, although further study is necessary. Finally, our results suggest that management practices should be tailored to each population, because environmental conditions may have different effects even on genetically similar groups.

Aim: Adult body size often exhibits patterns across large‐scale environmental gradients, creating ecogeographic clines. However, the form of body size clines varies across taxonomic groups, with linear and non‐linear patterns in body size observed in nature. Non‐linear body size clines have received less study, and questions remain about how environmental gradients interact to produce non‐linear clines. We examined the body size of the American horseshoe crab (Limulus polyphemus), a widely distributed marine arthropod, and evaluated the hypothesis that temperature and active season length can interact multiplicatively to result in a dome‐shaped distribution. Location: Fourteen states in the United States of America and three Mexican states, representing the entire geographic range of the species. Methods: We compiled environmental data and body size measurements from more than 49,000 individual horseshoe crabs. For each location, we extracted from the literature or calculated from raw data the mean male prosoma width and the mean female prosoma width. We applied a general additive modelling (GAM) approach to characterize the body size cline, test a hypothesis regarding temperature and season length, and explore evidence for the influence of additional environmental factors. Results: Model results indicate temperature and season length could act multiplicatively to produce dome‐shaped clines, and these findings align with and quantify previous anecdotal reports of a strong dome‐shaped body size cline across latitude for horseshoe crabs. Main Conclusions: Active season length appears to become relatively more influential on horseshoe crab body size in the northern part of their range, while temperature effects per se appear to dominate in southern latitudes. For horseshoe crabs, the pattern of size variation is consistent with the predictions of Optimal Resource Allocation models, but more study is needed to elucidate mechanistic underpinnings. Considering climate change projections, results from our study suggest future shifts in horseshoe crab body sizes. [ABSTRACT FROM AUTHOR]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2007.01.012 Byline: Rachel L. Schwab, H. Jane Brockmann Abstract: Satellite male horseshoe crabs form spawning groups around some nesting pairs (female plus attached male) while leaving others to nest alone. Furthermore, females of pairs that attract satellites are larger and lay more eggs than females of pairs that do not attract satellites. We experimentally tested whether satellite males use visual cues to discriminate among large and small females and if satellites use chemical cues from eggs to distinguish among females. We conducted experiments in the field in the northern Gulf of Mexico at Seahorse Key, FL, U.S.A. in which we observed the behaviour of satellite males as they approached cement models of horseshoe crab pairs. Satellites were significantly more likely to approach and join model pairs with large females than with small females. However, there was no difference in the length of time satellites remained joined to the models. When chemical cues were examined, there was no difference in the number of males that approached or joined identical female models with and without eggs. However, once a satellite joined, it remained attached significantly longer to the model pair with eggs underneath. This study shows that satellite male horseshoe crabs use multiple cues, first visual to locate nesting pairs, then chemical to decide whether to remain with a nesting female. Our results show that males that are approaching from the water use visual cues from the amount of exposed carapace to distinguish the size of females nesting on land, even when those females are well buried in the sand. Author Affiliation: Department of Zoology, University of Florida, U.S.A. Article History: Received 21 April 2006; Revised 20 September 2006; Accepted 15 January 2007 Article Note: (miscellaneous) MS. number: A10428

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2006.12.004 Byline: Laura K. Sirot, H. Jane Brockmann, Stephen L. Lapointe Abstract: For most species that have been studied, considerable variation exists in male postcopulatory reproductive success, including female sperm use, reproductive investment and remating patterns. We investigated postcopulatory sexual selection in the beetle Diaprepes abbreviatus (L.) (Coleoptera: Curculionidae) by examining the correlation of two measures of a male's success (proportion of eggs fertilized (P.sub.2) and number of eggs that a female laid after mating with him) with male body size, copulatory behaviour and copula duration. We allowed each female to mate with an irradiated sterile male and a normal male. Relative duration of intromission (i.e. the difference in the intromission durations of the two males) and relative stroking rate, but not the absolute duration and stroking rate, were positively correlated with P.sub.2. The number of eggs that a female laid was negatively related to the thrusting rate of her mate. Irradiated males mated for a shorter duration and thrusted at a lower rate than normal males. Irradiated males also fertilized a lower proportion of eggs than normal males, and females were more likely to remate after mating with an irradiated male than after mating with a normal male. These findings suggest that behavioural traits may influence male postcopulatory reproductive success. Furthermore, since variation in male stroking rate and intromission duration are associated with variation in male fertilization success, these traits may have evolved through postcopulatory sexual selection. Author Affiliation: (a) Department of Zoology, University of Florida, U.S.A. (a ) Department of Molecular Biology and Genetics, Cornell University, U.S.A. (a ) United States Department of Agriculture, Agricultural Research Services, United States Horticultural Research Laboratory, U.S.A. Article History: Received 28 April 2006; Revised 8 June 2006; Accepted 4 December 2006 Article Note: (miscellaneous) MS. number: A10433R

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2006.02.002 Byline: Manuel J. Velez, H. Jane Brockmann Abstract: Conspicuous male traits, such as calling to attract females, evolve through the joint action of sexual and natural selection. When the costs of natural selection increase relative to the benefits of sexual selection, males should become less conspicuous. Male calling song in field crickets attracts both phonotactic females for mating and acoustically orienting parasitic flies that deposit larvae on calling males, killing their infected hosts. Flies are present mainly during the autumn, which means that crickets that become adults at this time have a different selective regime from those that emerge in the spring. On this basis we hypothesized that seasonal changes in parasitism would favour seasonal changes in male calling behaviour. We evaluated this hypothesis by recording the calls of individual males and by conducting nightly surveys of male calling in the field. Because seasonal changes in sexual selection may favour seasonal changes in male calling behaviour, we used pitfall traps to determine whether the number of females attracted to male calls changed seasonally. As predicted, fewer males called during the autumn than during the spring, and autumn males were less likely to call at dusk, when flies were most active. Contrary to prediction, however, males that called spent more time calling per night in the autumn than in the spring. Pitfall trap data revealed that more calling per night resulted in more female arrivals in the autumn but not in the spring. This result suggests that males that call for long periods attract more females in autumn but not in spring. This means that seasonal variation in both natural and sexual selection has resulted in seasonal differences in male calling behaviour. Author Affiliation: Department of Zoology, University of Florida, Gainesville, U.S.A. Article History: Received 20 June 2005; Revised 12 September 2005; Accepted 6 February 2006 Article Note: (miscellaneous) MS. number: A10191R

A study on relationship between seasonal variation and male calling behavior during courtship in field cricket, Gryllus rubens, is presented.