Reproductive cycle of the lizard Sceloporus mucronatus with comments on intraspecific geographic variation

Sceloporus mucronatus is a viviparous lizard that inhabits high altitudes in central México. Lizards from Tecocomulco, Hidalgo, México, were collected monthly at 2500 m throughout one year. Macro- and microscopic evidence of gonads showed that both sexes reproduce synchronously during the fall. In males, after a short testicular quiescence in December, the recrudescence begins in winter (January) and continues through spring and summer (July), with maximum activity occurring from late summer to early fall (August–September). Regression takes place simultaneously with copulation during the fall (October–November). In females, vitellogenesis occurs during summer and fall (August–November), with ovulation in the fall (November–December). Gravid females were found throughout the winter, and parturition occurs during spring (May). Litter size was correlated with female snout–vent length. Female reproductive phenology of viviparous Sceloporus species seems to be highly conservative at different altitudes, but male reproductive phenology shifts between spring–summer (in populations higher than 2500 m) and summer–fall (in populations 2500 m or lower), as in the present study. The longer period of testicular recrudescence (January–July) in the studied population from Tecocomulco suggests plasticity in testicular activity.     

Sperm viability in the reproductive tract of females in a population of Sceloporus mucronatus exhibiting asynchronous reproduction

Asynchronous reproduction is a common phenomenon in high-elevation populations of lizards from Central México. Sperm storage in the reproductive tract of females is the mechanism for making oocyte fertilization possible. Our study addresses questions related to functional oviductal sperm storage of females mating on different dates throughout the reproductive season. A population of Sceloporus mucronatus with copulation in the summer and ovulation in the fall was chosen for this experiment. Eleven females that copulated in the field during June and 13 females that copulated in captivity during August were maintained in the laboratory until parturition. The number of pregnant females and the litter sizes produced in each experimental group were indicative of the viability of the stored sperm. Sperm stored in the reproductive tract of females were able to fertilize eggs after 4 months. No significant differences were found in the number of pregnant females between the 2 experimental groups nor in the litter sizes that they produced. We found that the amount of time sperm were held in the female reproductive tract (ca. 3 months) had no effect on the capacity of sperm to fertilize eggs. Histological examination of 8 oviducts collected before the mating season eliminated the possibility of sperm storage from one year to the next. In this system, sperm retention could have evolved as a response mechanism to deal with the asynchrony between sexes in the reproductive cycles. However, we cannot rule out alternative hypotheses.     

Bionomics of two aspen bark beetles, Trypophloeus populi and Procryphalus mucronatus (Coleoptera: Scolytidae)

Beetles of Trypophloeus populi attacked green bark of unhealthy aspen ( Populus tremuloides ) and hastened the death of the tree. Beetles of Procryphalus mucronatus favored dead bark and were of little significance in the death of the aspen. These two beetle species were distinguished from each other by their primary galleries, eggs, larvae, larval mines, and mating behavior. In T. populi, there were three larval instars and one to one and one - half generations per year; only larvae overwintered, and the eggs of the first generation were present by mid - July. In P. mucronatus, there were two larval instars and one and one - half to two generations per year; both larvae and adults overwintered, and the first eggs of the new season were present by late May.     

Lizards and turtles of western Chihuahua

This second report on the reptiles of Chihuahua deals with the lizards and turtles of western Chihuahua. Field work was done from 1956 to 1972 and was confined to the area west of Highway 45. General information pertaining to the ecology and geology reported in the section on snakes is not repeated. Ecological and life history information is included in the species accounts where data are available. In western Chihuahua 16 genera and 49 species and subspecies of lizards and 3 genera and 5 species of turtles are reported. Only one subspecies is described as new ( Sceloporus poinsettii robisoni ), and added data strengthen the diagnosis of others. Three genera ( Sceloporus, Cnemidophorus, and Eumeces ) contain 28 of the species and subspecies reported.     

Evolution of the sceloporine lizards (Iguanidae)

Phylogenetic relationships among Sceloporine genera are briefly discussed. Species relationships within the genus Sceloporus are analyzed, and evolutionary lines of descent are proposed. The genus Sceloporus is composed of three monophyletic groups: Group I, the most primitive, probably developed from Sator - like ancestral stock in Miocene times. This group speciated from stock similar to Sceloporus gadoviae in southern Mexico to S. merriami in the North and contains 7 species in 3 species groups. We propose that these species be included in the genus Lysoptychus Cope. Group II arose from Group I and evolved from centrally located Sceloporus pictus in all directions throughout Mexico. This intermediate group contains approximately 19 species in 5 species groups. Group III also arose from the primitive stock of Group I and radiated from several desert refugia created by Pleistocene glaciation. Evolution of this group in Mexico was generally from north to south with Sceloporus malachiticus extending as far south as Panama. This group contains approximately 33 species in 5 species groups.     

Numeric analysis of the lizard genus Sceloporus with special reference to cranial osteology

Phylogenetic relationships among Sceloporine genera are briefly discussed. Species relationships within the genus Sceloporus are analyzed, and evolutionary lines of descent are proposed. The genus Sceloporus is composed of three monophyletic groups: Group I, the most primitive, probably developed from Sator - like ancestral stock in Miocene times. This group speciated from stock similar to Sceloporus gadoviae in southern Mexico to S. merriami in the North and contains 7 species in 3 species groups. We propose that these species be included in the genus Lysoptychus Cope. Group II arose from Group I and evolved from centrally located Sceloporus pictus in all directions throughout Mexico. This intermediate group contains approximately 19 species in 5 species groups. Group III also arose from the primitive stock of Group I and radiated from several desert refugia created by Pleistocene glaciation. Evolution of this group in Mexico was generally from north to south with Sceloporus malachiticus extending as far south as Panama. This group contains approximately 33 species in 5 species groups.     

Status of Thamnophis sirtalis in Chihuahua, Mexico (Reptilia: Colubridae)

This is a study of the populations of Thamnophis sirtalis that occur in Chihuahua, Mexico, and the adjoining U.S. state of New Mexico. Reference is made to previous studies dealing with geographical and systematic relationships. Additional data are provided for the New Mexico subspecies ( dorsalis ), and the relationship of T. s. parietalis to the New Mexico population is discussed. The Chihuahua population is described as a new subspecies.     

Range expansion of the collared peccary in New Mexico: potential for interactions between historically separate subspecies

The collared peccary ( Tayassu tajacu ) is undergoing range expansion in the southwestern United States. Here we report sightings of the collared peccary from locations outside the known ranges of either of the subspecies, T. t. sonoriensis and T. t. angulatus , in south central New Mexico. Sightings include multiple individuals of different ages. This indicates that the collared peccary is expanding into previously unoccupied areas between the documented ranges of the 2 subspecies. We suggest that the possibility of gene flow between the 2 historically separate subspecies may have important evolutionary consequences.     

Demography of the Yarrow's spiny lizard, Sceloporus jarrovii , from the central Chihuahuan Desert

The demography of a population of Yarrow's spiny lizard, Sceloporus jarrovii , was examined from 2004 to 2006 in the canyon Las Piedras Encimadas, located in Gomez Palacio, Durango, México. Lizards were studied using a mark-recapture technique. Reproduction in females occurred between November and May, coinciding with dry conditions. Reproductive activity was highest (percent of females with vitellogenic follicles or embryos) in the middle of the dry season (November and December). Thirteen percent of females reached sexual maturity at an average age of 8.5 months. The population structure was similar in spring and fall, but not in summer. A notable feature of summer, coinciding with the wet season, was the greater number of hatchlings and juveniles. The overall sex ratio did not differ from 1:1. The density of adults varied from 12 to 62 animals ? 0.5 ha –1 . Temperate and arid-adapted populations of S. jarrovii exhibited broad similarity in timing of the reproductive season, whereas factors such as density, growth, age at sexual maturity, and survivorship differed.     

Contributions to the concepts of reproductive cycles and the systematics of the scalaris group of the lizard genus Sceloporus

The concept of parity type is proposed as a criterion of relationship among members of the Sceloporus aeneus – scalaris complex, with members of S. aeneus being regarded as viviparous and those of S. scalaris, as oviparous. The viviparous S. goldmani is regarded as a relative of S. aeneus, and S. a. subniger is not regarded as intermediate between S. scalaris and S. aeneus. The proposal by Davis and Smith that S. a. aeneus is oviparous and specifically distinct (as S. aeneus ) from S. a. bicanthalis (as S. bicanthalis ) is rejected. S. aeneus is hypothesized to have a biennial reproductive cycle. S. scalaris slevini auctorum is segregated into two subspecies: S. s. samcolemani subsp. nov. in the Sierra Oriental (northern end), and S. s. slevini sensu stricto in the Sierra Occidental (also northern end) of Mexico and of the adjacent United States.     

Mitochondrial genetic variation within and between Holbrookia lacerata lacerata and Holbrookia lacerata subcaudalis,the spot-tailed earless lizards of Texas

ABSTRACT

We examined genetic relationships among individuals and populations of the species Holbrookia lacerata, the spot-tailed earless lizard, using whole mitochondrial genomes. Lizards were collected from south, central and west Texas. We found significant amounts of genetic structure among populations and evidence of two major reciprocally monophyletic groups of spot-tailed earless lizards in Texas. Holbrookia lacerata lacerata occurs on the Edwards Plateau and adjacent regions of West Texas north of the Balcones Escarpment, while Holbrookia lacerata subcaudalis occurs in South Texas and adjacent Mexico south of the Balcones Escarpment. These two recognised subspecies correspond to the two clades we discovered. Holbrookia l. lacerata occupies much of its historical range at sometimes high population densities, while populations of H. l. subcaudalis appear to be highly fragmented based on recent observations compared to their historical range.     

Sexual dimorphism of body size in taxidermy specimens of Equus quagga quagga Boddaert (Equidae)

ABSTRACT

Mare taxidermy specimens of quaggas (Equus quagga quagga, an extinct subspecies of the plains zebra that was endemic to South Africa) are significantly longer and marginally taller than stallions – unlike the situation in extant subspecies of plains zebras where the stallions are usually larger than the mares. The possibilities that these differences were due to sampling error, shrinkage of the hides, or distortion during specimen mounting are addressed. It is likely, however, that the taxidermy specimens reflect a sexual dimorphism that existed in quaggas. Differences in body size between mares and stallions might have been an adaptation to their comparatively cold and arid environment, or it might have been caused by genetic drift in a geographically isolated population, or it might have been brought about by a combination of these circumstances.     

Growth rates of wild green turtles,Chelonia mydas,at a temperate foraging habitat in the northern Gulf of Mexico: assessing short‐term effects of cold‐stunning on growth

There are multiple factors that may determine individual and population growth rates and understanding the impact of extrinsic factors, such as temperature, is important for successful recovery plan stock assessment and modelling. In January 2001 and January 2003, cold‐stunning events occurred along the northern Gulf of Mexico, in St Joseph Bay, Florida. In this study we examine the short‐term effects of decreased water temperatures and repeated cold‐stunning events on the growth of juvenile green turtles in northwest Florida. There were no significant effects of number of cold‐stunning events on growth, although turtles stunned twice tended to grow slower than non‐stunned turtles. This is the first study to provide information on the growth rates of green turtles in the northern Gulf of Mexico and it is the first examination of the effects of cold‐stunning on growth in any sea turtle population.     

A quantitative survey of the aquatic invertebrate community in the “Monumento natural Salar de Surire” on the Chilean Altiplano

A quantitative survey of the aquatic invertebrate community at a salar on the Chilean Altiplano is described. To establish the taxonomic composition and abundance we monitored inter-annual changes in community structure for four consecutive years covering different conditions. The community was composed of 21 taxa, representing 16 families, and was mainly dominated by arthropods. We found a high number of endemic species compared to other freshwater systems despite the low abundances detected. There were statistically significant inter-annual differences in diversity. A canonical correlation indicated that species richness was mainly affected by temperature. We studied this unique system by taking advantage of the “natural laboratory” that it offers. We found a combination of eutrophic conditions with low species diversity at the consumer level. This system invites further research on the community dynamics and microevolutionary aspects of invertebrate populations.     

Biogeographic and taxonomic relationships among the mountain snails (Gastropoda: Oreohelicidae) of the central Great Basin

Described here are 4 species of mountain snails, Oreohelix , isolated on mountains in the central Great Basin of Nevada and Utah since the end of the Pleistocene. Forty-three mountains were searched during an 18-year period, resulting in 24 mountains found with no oreohelicids present. One population, Oreohelix loisae (19 mm to 23 mm in shell diameter), is described here as a new species related to, but geographically isolated from, the species Oreohelix nevadensis (17 mm to 22 mm diameter). Oreohelix loisae is present only in the Goshute Mountains while O. nevadensis is represented in 3 geographically adjacent ranges in the central Great Basin. These 2 species are possibly related to the Oreohelix haydeni group from the northern Wasatch Range. The subspecies Oreohelix strigosa depressa (15 mm to 21 mm diameter) is present on 11 ranges from western Utah west to east central Nevada. This subspecies is closely related to populations found today in the northern Wasatch Mountains of Utah. The smallest species in diameter (8 mm to 14 mm), Oreohelix hemphilli , is centered in the central Great Basin and found on 16 ranges often in sympatry with 1 or 2 of the larger conspecifics. Both qualitative and quantitative information on shell characters and soft anatomy is provided here for these 4 species. Shell characters, soft anatomy, geographical isolation, and statistical analysis suggest that 4 distinct species inhabit the central Great Basin today. Xeric and calciphilic species include O. hemphilli and O. loisae , while O. strigosa and O. nevadensis typically are associated with permanent water and both metamorphic and limestone mountains.     

Homing in eastern fence lizards ( Sceloporus undulatus ) following short-distance translocation

We conducted an experiment on eastern fence lizards ( Sceloporus undulatus ) during August-September 1995 near Los Alamos, New Mexico, (1) to ascertain if lizards that were relocated short distances exhibited homing, (2) to investigate a possible barrier to movement, and (3) to determine the effect of translocating individuals from a transplant area on lizards in a recipient area. We relocated 15 of an estimated population of 39 (95% CI 36-45) lizards an average distance of 46 m. Fourteen of 15 translocated lizards returned to within 6.81 ( s ￣x = 1.43) m of the original capture location. Movement distances did not vary ( F = 0.76; 1,53 df; P = 0.381) between resident and translocated lizards during the pretreatment period and did not vary for resident ( F = 2.86; 1,12 df; P = 0.1166), but varied between pretreatment and posttreatment periods for translocated ( F = 14.65, 1,7 df, P 0.0065) lizards. Translocated lizards did not affect the resighting probability of resident lizards ( F = 0.96; 1,14 df; P = 0.34), but this may be related to low power (1 — β = 0.15) and translocated lizards moving out of the area quickly.     

Demography of Astragalus scaphoides and effects of herbivory on population growth

Losses in fecundity due to predispersal herbivory can be large; however, the effects of this loss on long-term population viability have rarely been investigated. I conducted a demographic study of Astragalus scaphoides (Fabaceae), a long-lived perennial endemic to east central Idaho and adjacent Montana, by following mapped individuals at two sites from 1986 to 1993. Astragalus scaphoides suffers losses of predispersal fecundity averaging nearly 50% from insect seed predation and inflorescence predation by insects and livestock. Cattle reduced fecundity by 0-85%. Nonetheless, estimates from matrix projection models indicate that both sample populations had positive growth in most years. Elasticity analyses revealed that population growth occurred in spite of relatively small contributions by recruitment compared to growth and survival of nonreproductive plants. Results suggest that populations of this long-lived perennial depend little on reproduction and recruitment for growth and can persist in association with seasonal-rotation livestock grazing.     

A new subspecies of the snake Lichanura trivirgata from Cedros Island, Mexico

A new subspecies, Lichanura trivirgata bostici, from Cedros Island, Baja California del Norte, Mexico, is described, figured, and compared to other taxa of the genus.     

Conservation, status, and life history of the endangered White River spinedace, Lepidomeda albivallis (Cyprinidae)

Lepidomeda albivallis (White River spinedace), a fish species endemic to the White River, Nevada, appeared headed toward extinction. In 1991 only 1 population remained, and it comprised fewer than 50 individuals in a 70-m stream reach. We monitored population recruitment and distribution and studied life history and habitat use from 1993 through 1998. We determined that L. albivallis was not reproducing and was continuing to decline, and as an emergency measure we relocated the population (14 in spring 1995 and 6 in spring 1996) downstream 200 m to a secure habitat that we judged more favorable for reproduction. The relocated population reproduced, and by September 1998 it had increased to 396 individuals that inhabited more than 1 km of stream including both pond and stream habitats. In streams they oriented near the bottom but frequently moved up in the water column to strike at drift items. Gut analysis of museum specimens indicated L. albivallis is omnivorous but feeds primarily upon aquatic invertebrates. Conservation of L. albivallis will require reestablishing additional populations within its former range.