Rodrigo Macip-Ríos

Evidence of Pelvic and Nonpelvic Constraint on Egg Size in Two Species of Kinosternon from Mexico

Abstract Optimal egg size theory predicts that natural selection optimizes egg size within populations and most of the variation in reproductive output is attributable to clutch size variation driven by body size, available resources, and age. For small-bodied turtles, morphological (pelvic) constraint on egg size has been considered the main explanation when populations exhibit considerable variation in egg size, because the pelvis could be under selection for other functions besides reproduction. Kinosternids, a small-bodied and semiterrestrial lineage of turtles, show evidence for both pelvic and nonpelvic constraint on egg size. In order to test if small species show a tendency toward pelvic constraint on egg size, we examined possible pelvic constraints in 1 population of the small-bodied Kinosternon chimalhuaca from western Mexico and in 3 populations of medium- to large-bodied Kinosternon integrum from central Mexico. Gravid females were X-rayed to measure both pelvic aperture and egg width. To test for pelvic constraint on each population we compared the slopes of pelvic aperture and egg width (mean and maximum) to body size (plastron length) with analysis of covariance (ANCOVA); we also compared egg elongation with fresh egg measurements among populations using ANCOVA (with body size as covariate), and we conducted an allometric analysis in order to test for egg size optimization. We found evidence of pelvic constraint in 1 population of K. integrum, and evidence of nonpelvic constraint in the K. chimalhuaca population and in the other 2 populations of K. integrum. Our data did not support the supposed adaptive compromise and pelvic constraints on egg size in small-bodied turtles reported in other studies. Environmental factors such local pressure on egg size (stability of the environment) could explain this pelvic constraint discrepancy in kinosternids.

Population ecology and reproduction of the Mexican mud turtle ( Kinosternon integrum ) in Tonatico, Estado De México

ABSTRACT. Ecological data directly from the field are important in understanding the life history strategies of kinosternid species in the tropics. Herein we summarize the basic population ecology and life history of Kinosternon integrum in the municipality of Tonatico (southeastern Estado de México, México). From October 2003 to November 2004, we marked a total of 204 turtles and recaptured 118 of them. Mean population size using the Jolly-Seber model was 197 (95% CI 128–416) individuals, with a sex ratio of 1:1.7, biased to females. Males were larger than females in carapace length and plastron length. The reproductive season starts in late June and finishes in late October. The smallest female with oviductal eggs was 122 mm in carapace length. Mean clutch size was 4 eggs (s = 1.77, range 1–8) and was significantly and positively related to body size. Mean egg length was 30.43 mm (s = 2.24, range 23.92–35.96), mean width was 16.35 mm (s = 1.01, range 12.99–18.30), and mean weight was 5.14 g (s = 0.60, range 3.41–6.57). Mean egg length was significantly and inversely related to clutch size. Relative clutch mass (reproductive effort) was 0.043 (s = 0.017, range 0.017–0.071), which is the smallest value reported for the genus Kinosternon. Additionally, there was no evidence of a pelvic restriction on egg size in this population. This is the first study that documents basic population ecology and reproductive characteristics for a single population of the most widespread freshwater turtle in Mexico.

Evidence for the morphological constraint hypothesis and optimal offspring size theory in the Mexican mud turtle (Kinosternon integrum).

Optimal offspring size theory states that natural selection should balance reproductive output by optimizing between offspring size and offspring number. If a species has evolved an optimal offspring size, the fitness of larger females should be increased by simply producing more offspring of an optimum size. In contrast, when offspring size is not optimized, the morphological constraint hypothesis may apply, and in this case, maternal fitness is increased by producing the greatest number of the largest offspring that mothers are physically capable of producing. We used a log-log allometric regression approach on clutch size, egg size, and body size data to test the application of optimal offspring size theory and the morphological constraint hypothesis in the Mexican mud turtle (Kinosternon integrum) in southern Mexico. Our results indicate that this turtle seems to follow the morphological constraint hypothesis when all data are analyzed together, but when data are divided between small (< 140 mm plastron length) and large females (> 140 mm plastron length), optimal offspring (egg) size theory was supported only in large females, while the morphological constraint hypothesis was supported in small females. Our results thus indicate that K. integrum females may increase their fitness in two different, size-dependent ways as they grow from size at sexual maturity to maximum body size.

Effects of Climate Change in Amphibians and Reptiles

During the past decade it has been documented that the average of earth temperature increased 6 °C in a period of 100 years. The higher amount of this phenomenon has been recorded between 1910 and 1945 and, from 1976 to present date (Jones, 1999; Kerr, 1995; Oechel et al., 1994; Thomason, 1995). From 1976 to present the temperature rising has been the faster recorded in the last 10,000 years (Jones et al., 2001; Taylor, 1999; Walther et al., 2002), and this caused the maximum daily temperature increase in the southern hemisphere (Easterling et al., 2000), as well as a significant temperature increase in the tropical forest areas (Barnett et al., 2005; Houghton et al., 2001; Santer et al., 2003; Stott, 2003). According to projections, the average temperature of earth may increase up to 5.8 °C (Intergovernmental Panel on Climate Change IPCC, 2007) at the end of current century, which actually represents and enormous threat for biodiversity (Mc Carty, 2001; Parmesan & Yohe, 2003). Although the historical data describes a changing climate during the last 350 million years of amphibians and reptiles history (Duellman & Trueb, 1985), the abrupt rising of the temperature during the last century could have a great impact on ectotherm organisms, which depend of environmental temperature to achieve physiological operative body temperatures (Walter et al., 2002; Zachos et al., 2001). Thus, the accelerated grow of earth temperature could affect physiological, reproductive, ecological, behavioral, and distribution traits among amphibians and reptiles (Cleland et al., 2006; Dorcas et al., 2004; Pough, 2001; Gvozdik & Castilla, 2001). In this context, a review of the published studies is necessary to evaluate and summarize the evidence of climate change effects in amphibians and reptiles. This review should provide an overview that should be helpful for researches, students, and policy makers, in order to address how climate change affects amphibians and reptiles, and the possible responses of these organisms to climate change. Due to the available published information are not equal for amphibians and reptiles, the present chapter are divided in two: amphibians and reptiles. In each chapter subdivision a physiological, reproductive, and distribution effects are issued as long as information was available. Additional information in amphibians such as synergic effects of environmental factors due climate change, and evolutionary adaptations are addressed. At the end of the chapter a conclusion section is added in order to summarize the most important trends addressed in this review.

Alimentary Habits of the Mexican Mud Turtle (Kinosternon integrum) in Tonatico, Estado de México

Abstract Alimentary habits are critical to the ecology of all animals. They reflect resource availability and are correlated with important life history traits such as reproductive output and body size. We analyzed the diet of the previously unstudied Mexican mud turtle Kinosternon integrum at Tonatico, Estado de México, during 2003 and 2004. Analysis was conducted separately by sex and age (immature vs. adults) and seasons (rainy vs. dry). Gastric contents and fecal samples were used in combination for more complete results. Based on 57 samples (32 stomach flushes and 25 from feces), K. integrum is a generalist–opportunist in alimentary habits, feeding on 27 categories of food. Plant material, Coleoptera, Odonata, Diptera, and mixed animal matter were the most important components. Overall dietary diversity was similar between adults and juveniles and between the two sexes, but juveniles differed between seasons. In similarity analysis we found a shift in diet between seasons. Females shifted from being primarily carnivorous during the rainy season to being primarily herbivorous during the dry season, while males were carnivorous during both seasons. The data suggest that this turtle feeds opportunistically on available prey items rather than on a few preferred food items.

First record of Orbopercularia lichtensteini (Peritrichia: Operculariidae) attached to a hemipteran, Corisella edulis (Nepomorpha: Corixidae), in Hidalgo, Mexico, with notes on its cytology and distributional patterns

ABSTRACT Operculariidae includes sessile ciliate species mainly attached to diverse substrates, but records are scarce for their attachment to aquatic true bugs. The goal of this contribution is to provide new cytological data with optical and scanning electron microscopy of Orbopercularia lichtensteini, and some notes about their distribution on a Mexican corixid. We manually collected the corixids in a pond in Mexico during a six-month period, and all individuals were revised to observe the peritrichids. We calculated the abundance and prevalence, with an emphasis on the specific micro-location of the epibiotic peritrich on the host Corisella edulis. A total of 36,205 peritrichids were recorded in 158 corixids. The colonies with fine striated zooids were dichotomously branched and mostly attached to left eyes, but also on other body regions, i.e. left wings and rostrum. We conclude that some morphological colony traits bring some advantages for food particle capture, and aspects of the biology and morphology of Corisella edulis play an important role in determining the spatial distribution of O. lichtensteini.