Aspidoscelis costatus costatus (Squamata, Teiidae): high elevation clutch production for a population of whiptail lizards

Clutch size and number of clutches per reproductive cycle are important life history traits that can be influenced by anatomical, physiological, evolutionary, and ecological factors. This report on the clutch size and number of clutches of an endemic Mexican whiptail lizard, Aspidoscelis costatus costatus (Cope, 1878), is based on a study of population at an unusually high elevation for a member of this genus. The study site is located in Ixtapan de la Sal, southeastern Estado de México, Central Mexico, at 2090 m a.s.l. Lizards were sampled in June 2006, and from May to July 2007, where females of Aspidoscelis costatus costatus were collected by hand along a drift fence. Female reproductive condition was evaluated based on abdominal palpation for presence of developing eggs; clutch size was determined by actual counts of either vitellogenic follicles or oviductal eggs. The smallest reproductive female was 77 mm snout-vent length; females produced a minimum of two clutches during the breeding season, the mean clutch size of 6.5 eggs (n = 33) was one of the largest reported for the genus. However, both length and width of its eggs, and the relative clutch mass have not been diminished by development of a large clutch. Additionally, comparisons of clutch size were undertaken within the polytypic A. costatus complex, within the genus Aspidoscelis, and between certain genera of whiptail lizards. This apparently represents the first study of whiptail lizards (genus Aspidoscelis), assessing the aforementioned reproductive characteristics, in a population above 2000 m.

Reproductive biology of Hybopsis amblops, the Bigeye Chub, in the Flint River of Alabama

Background. The purpose of this study was to establish a reproductive schedule and examine reproductive traits that shape fecundity of the Bigeye Chub, Hybopsis amblops Cyprinidae, in the Flint River system of north Alabama. Methods. Life history traits associated with reproduction, growth, and maturation were assessed. Fish collections were made monthly from August, 2013, through July, 2014. Results. The Bigeye Chub in Alabama primarily spawns in April and May as indicated by gonadosomatic index (GSI), ovarian condition and clutch size. Average GSI values began to rise in February, peaked in April and May at over 13% for females and 1.6% for males, and showed a steep decline from May to June for both sexes. Average clutch size was highest in April at 812. Diameter of the most mature oocyte stage averaged 0.74 mm, relatively small compared to other cyprinids found in the Flint River. Discussion. The Bigeye Chub’s relatively large clutch size as a measure of fecundity places the species intermediate between opportunistic and periodic in the trilateral life history scheme of Winemiller and Rose. The species is apparently responding to a flow regime with a defined seasonality as well as predictability of flow and resources.

Reproductive biology of Hybopsis amblops, the Bigeye Chub, in the Flint River of Alabama

Background. The purpose of this study was to establish a reproductive schedule and examine reproductive traits that shape fecundity of the Bigeye Chub, Hybopsis amblops Cyprinidae, in the Flint River system of north Alabama. Methods. Life history traits associated with reproduction, growth, and maturation were assessed. Fish collections were made monthly from August, 2013, through July, 2014. Results. The Bigeye Chub in Alabama primarily spawns in April and May as indicated by gonadosomatic index (GSI), ovarian condition and clutch size. Average GSI values began to rise in February, peaked in April and May at over 13% for females and 1.6% for males, and showed a steep decline from May to June for both sexes. Average clutch size was highest in April at 812. Diameter of the most mature oocyte stage averaged 0.74 mm, relatively small compared to other cyprinids found in the Flint River. Discussion. The Bigeye Chub’s relatively large clutch size as a measure of fecundity places the species intermediate between opportunistic and periodic in the trilateral life history scheme of Winemiller and Rose. The species is apparently responding to a flow regime with a defined seasonality as well as predictability of flow and resources.

Reproductive biology of Hybopsis amblops, the Bigeye Chub, in the Flint River of Alabama

Background. The purpose of this study was to establish a reproductive schedule and examine reproductive traits that shape fecundity of the Bigeye Chub, Hybopsis amblops Cyprinidae, in the Flint River system of north Alabama. Methods. Life history traits associated with reproduction, growth, and maturation were assessed. Fish collections were made monthly from August, 2013, through July, 2014. Results. The Bigeye Chub in Alabama primarily spawns in April and May as indicated by gonadosomatic index (GSI), ovarian condition and clutch size. Average GSI values began to rise in February, peaked in April and May at over 13% for females and 1.6% for males, and showed a steep decline from May to June for both sexes. Average clutch size was highest in April at 812. Diameter of the most mature oocyte stage averaged 0.74 mm, relatively small compared to other cyprinids found in the Flint River. Discussion. The Bigeye Chub’s relatively large clutch size as a measure of fecundity places the species intermediate between opportunistic and periodic in the trilateral life history scheme of Winemiller and Rose. The species is apparently responding to a flow regime with a defined seasonality as well as predictability of flow and resources.

Reproductive biology of Hybopsis amblops, the Bigeye Chub, in the Flint River of Alabama

Background. The purpose of this study was to establish a reproductive schedule and examine reproductive traits that shape fecundity of the Bigeye Chub, Hybopsis amblops Cyprinidae, in the Flint River system of north Alabama. Methods. Life history traits associated with reproduction, growth, and maturation were assessed. Fish collections were made monthly from August, 2013, through July, 2014. Results. The Bigeye Chub in Alabama primarily spawns in April and May as indicated by gonadosomatic index (GSI), ovarian condition and clutch size. Average GSI values began to rise in February, peaked in April and May at over 13% for females and 1.6% for males, and showed a steep decline from May to June for both sexes. Average clutch size was highest in April at 812. Diameter of the most mature oocyte stage averaged 0.74 mm, relatively small compared to other cyprinids found in the Flint River. Discussion. The Bigeye Chub’s relatively large clutch size as a measure of fecundity places the species intermediate between opportunistic and periodic in the trilateral life history scheme of Winemiller and Rose. The species is apparently responding to a flow regime with a defined seasonality as well as predictability of flow and resources.

Evidence for r - and K -selection in a wild bird population: a reciprocal link between ecology and evolution

Understanding the variation in selection pressure on key life-history traits is crucial in our rapidly changing world. Density is rarely considered as a selective agent. To study its importance, we partition phenotypic selection in fluctuating environments into components representing the population growth rate at low densities and the strength of density dependence, using a new stochastic modelling framework. We analysed the number of eggs laid per season in a small song-bird, the great tit, and found balancing selection favouring large clutch sizes at small population densities and smaller clutches in years with large populations. A significant interaction between clutch size and population size in the regression for the Malthusian fitness reveals that those females producing large clutch sizes at small population sizes also are those that show the strongest reduction in fitness when population size is increased. This provides empirical support for ongoing r - and K -selection in this population, favouring phenotypes with large growth rates r at small population sizes and phenotypes with high competitive skills when populations are close to the carrying capacity K . This selection causes long-term fluctuations around a stable mean clutch size caused by variation in population size, implying that r - and K -selection is an important mechanism influencing phenotypic evolution in fluctuating environments. This provides a general link between ecological dynamics and evolutionary processes, operating through a joint influence of density dependence and environmental stochasticity on fluctuations in population size.

Reporte del tamaño de una camada de barisia imbricata (wiegmann, 1828) (reptilia: anguidae)

The genus Barisia is endemic to Mexico occurring in temperate regions, at elevations between 2200-3800 m above sea level. Few records of clutch size of the species of Barisia are available, in particular for B. imbricata. The first report of a large clutch size (15 neonates alive) is given for this species.

Parasite infestation and predation in Darwin's small ground finch: contrasting two elevational habitats between islands

Contrasting ecological conditions may affect the distribution, abundance and impact of parasites and predators throughout the ranges of hosts and prey. Such patterns are evident on the archipelagos of Hawaii and the Galapagos, which vary in their distribution and abundance of avian parasites within and across islands. Previous research has documented higher intensity of parasitic fly larvae (Philornis downsi) in nests of Darwin's finches on elevated islands of the Galapagos. Here we examine P. downsi intensity and predation in 71 nests of Darwin's small ground finch (Geospiza fuliginosa) on Floreana Island. We found significant differences in parasite intensity, nest predation and clutch size between the lowland (0–100 m) and highland (300–400 m) habitats. Lowland finch nests had few P. downsi parasites (mean of 8 per nest), high nest predation (44% of nests) and large clutch size (3.4). Highland finch nests showed the opposite pattern, with many P. downsi parasites (40 per nest), low nest predation (17%) and small clutch size (2.5). This study suggests that the impacts of an introduced parasite are limited by its niche requirements and resource availability within and across islands. Our findings also imply that the vulnerability of bird populations to introduced parasites and predators is linked with variation in life history strategies across habitats.

Costs of reproduction in a long-lived bird: large clutch size is associated with low survival in the presence of a highly virulent disease

Fitness costs of reproduction are expected to be more pronounced when the environmental conditions deteriorate. We took advantage of a natural experiment to investigate the costs of reproduction among common eiders ( Somateria mollissima ) nesting at a site in the Arctic, where an avian cholera epizootic appeared at different magnitudes. We tested the predictions that larger reproductive effort (clutch size) is associated with lower survival or breeding probability the following year, and that this relationship was more pronounced under heightened exposure to the disease. Our results indicate that large clutch sizes were associated with lower survival of female eider ducks, but only when there was heightened exposure to avian cholera, as indexed by eider mortality on site. No cost was observed when cholera was absent or when lesser exposure was evident. This supports the hypothesis that fitness costs of high reproductive effort are higher under unfavourable conditions such as a disease epizootic, and further indicates that being a conservative breeder can increase survival probability, given the presence of a highly virulent disease.

Avian Paternal Care Had Dinosaur Origin

The repeated discovery of adult dinosaurs in close association with egg clutches leads to speculation over the type and extent of care exhibited by these extinct animals for their eggs and young. To assess parental care in Cretaceous troodontid and oviraptorid dinosaurs, we examined clutch volume and the bone histology of brooding adults. In comparison to four archosaur care regressions, the relatively large clutch volumes ofTroodon, Oviraptor, andCitipatiscale most closely with a bird-paternal care model. Clutch-associated adults lack the maternal and reproductively associated histologic features common to extant archosaurs. Large clutch volumes and a suite of reproductive features shared only with birds favor paternal care, possibly within a polygamous mating system. Paternal care in both troodontids and oviraptorids indicates that this care system evolved before the emergence of birds and represents birds' ancestral condition. In extant birds and over most adult sizes, paternal and biparental care correspond to the largest and smallest relative clutch volumes, respectively.