摘要:

We present an initial evaluation of relationships among a diverse sample of 215 species of snakes (8% of the world snake fauna) representing nine of the 16 commonly‐recognized families. Allelic variation at four slow‐evolving. protein‐coding loci, detected by starch‐gel electrophoresis, was found to be informative for estimating relationships among these species at several levels. The numerous alleles detected at these loci [Arp‐2 (42 alleles).Ltlh‐2 (43),Mdh‐1 (29),Pgm(Z)] provided unexpected clarity in partitioning these taxa. Most congeneric species and several closely‐related genera have the same allele at all four loci or differ at only a single locus. At thc other extreme are those species with three or four unique alleles; these taxa cannot be placed in this analysis. Species sharing two or three distinctive alleles are those most clearly separated into clades. Typhlopids, pythonids, viperids, and elapids were resolved into individual clades. whereas bods were separated into boincs and erycines, and colubrids appeared as scveral distinct clades (colubrines, natricines, psammophines, homalopsines, and xenodontines). Viperids were recognized as a major division containing three separate clades: Asian and American crotalines. Pabearctic and Oriental viperines, and Ethiopian causines. The typhlopids were found to be the basal clade, with the North American erycine boid Chrrrino and the West Indian woodsnakes Tropidophi, Y near the base. A number of species and some small clades were not allocated because of uninformative (common, unique, or conflicting) alleles. Of the 21 S species examined, five to eight appear to have been misplaced in the analysis of these elect

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05482.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

We investigated changes in the reproductive output and the effect of female phenotype on reproductive parameters in a shield bugElasmostethus interstinctus(L.) (Heteroptera: Acanthosomatidae) over the whole reproductive period. At the beginning and the middle of the reproductive period eggs were smaller than at the end of the period. Clutch mass and number of eggs per clutch decreased in laying sequence, first clutches being much larger than any of the later ones. Lifetime fecundity correlated positively with female size: large females produced more eggs and lived longer than small ones. Egg size did not vary with female size. Offspring survival until adulthood increased with egg weight. Individuals overwinter before reproduction, and because the nymphs from later‐laid eggs have the least time to gather resources before overwintering, it may be important for later‐laid eggs to be of high quality. Reproductive allocation varies during the reproductive period; females allocate resources relatively more to offspring number at the beginning of the reproductive period and more to offspring quality at the end of their l

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05483.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The sexual strategies of salamanders are largely‘unobservable’owing to the low visibility typical of their preferred breeding habitats. We conducted both field and laboratory studies to investigate the sexual strategy of the North American central long‐toed salamander,Ambystoma macrodactylum columbianum.Capture‐recapture and cohort‐marking of salamanders at an aquatic breeding site indicated that males arrive before females and remain in the water for longer periods of time (measured in weeks, rather than days as for females). We estimate that the overall duration of the breeding season is short, three weeks or less. Courtship between single males and females is characterized by repeated bouts of axillary amplexus, separated by multiple episodes of spermatophore deposition. Amplectant males provide females with considerable tactile stimulation in the form of head‐rubbing. Unpaired males attempt to displace amplectant males from their partners by wrestling with them. In addition, unpaired males appear to interfere in ongoing courtship encounters during the spermatophore deposition stage, perhaps attempting to 'steal’inseminations. We suggest that explosive scramble‐competition polygyny best describes the mating system ofA. m. columbianum.Operational sex ratios are probably male‐biased throughout the short breeding season, leading to intense competition among males for mates. Mate choice (by either sex) probably is of little importance as a determinant

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05484.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

We studied the effect of hatching date on breeding performance (chick growth and mortality) and phenology (creching and fledging ages) of the chinstrap penguin during three years. The year affected every variable considered, probably due to pack‐ice persistence and food availability differences between years. Hatching date had slight or no effect on mortality and early growth, but was negatively correlated with creching age, which, in turn, was positively related to final size. The decision to leave the chicks unguarded does not seem to be based on the condition of the chicks, but on that of adults. Fledging age was negatively correlated with hatching date, and this effect was more marked in the year with poor growth performance. Given the short time available for breeding in Antarctica, there must be conflicting pressures between investing in feeding chicks and advancing the period of premoult resource storage, this explaining the strong relationship between hatching dates and subsequent phenological events (creching and fledging). In this kind of study, it may be important to remove the effect of inter‐year variation before assessing the possible effects of other variab

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05485.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Dispersal in slender‐tailed meerkats or suricates, Suricata suricatta, in the south‐western Kalahari occurred mainly during the early breeding season, and was age‐ and sex‐dependent. Among yearlings, more males than females were immigrants, but more females than males disappeared. There were no sex differences in dispersal among two‐year‐olds, but among animals aged three years or older, more males than females emigrated. Most dispersers moved into adjacent bands or joined other transients, and females apparently suffered higher rates of mortality than males. Kinship with the same‐sex or opposite‐sex breeder had no discernible effect on the likelihood of dispersing. Both males and females madeprospecting foraysto other groups, apparently to assess dispersal and breeding opportunities. Males made frequent and repeated forays, often in coalitions with other band members or transients, whereas prospecting by females was generally solitary, and they were not known to make multiple forays. Prospecting males successfully took over dominance of two bands, and attempted to take over bands on three other occasions. Animals attempting to join or follow a band (trailers) behaved submissively and were readily chased by residents, whereas those attempting a dominance takeover (invaders) scent‐marked at a high rate and showed no submissive behaviours. Dispersing meerkats maximized reproductive success by increasing their mating opportunities, while animals which delayed dispersal received indirect benefits by hel

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05486.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Poison frogs (Family Dendrobatidae) are common leaf litter inhabitants of New World tropical rainforests. The name of this group derives from several genera (especiallyDendrobates, Minyobates,andPhyllobates) that are aposematically coloured and have toxic skin to varying degrees. Other species in the family, primarily the genusColostethus,are cryptically coloured and non‐toxic. Recent studies have revealed that the toxic compounds in the skin, which are lipophilic alkaloids, may have a dietary origin. Diets and associated characteristics, prey size, prey number, and niche breadth, of nine species in five genera, three of which have poisonous species, were examined. Interpretation of these characteristics in light of an independently constructed cladogram revealed the inclusion of a high percentage of Formicidae (ants) in the diets of toxic species. Although alkaloids have been reported in several insect groups, more alkaloids are known from ants than any other group. Species in the genusDendrobates, which are poisonous and have many other derived characters, have diets composed of 50–73% ants, whereas percentages of ants used by non‐toxic species in the genusColostethuswas 12–16%. Ants are the major prey category consumed by the five poisonous species considered in this study. In general, frogs separated into two groups. More basal groups with non‐toxic skin and cryptic coloration had diets with low percentages of ants, low numbers of prey per individual, and high niche breadths, indicating inclusion of a broad range of prey categories in their diets. Species with poisonous skin and aposematic coloration had diets with large percentages of ants, large numbers of prey per individual, and low niche breadths, indicating diets with relatively few prey categories. Thus, diet, and the subsequent evolution of uptake systems for alkaloids, may be the primary character that led to the development of toxic skin and permitted aposematism, leading to radiation of poisonou

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05487.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Reproductive behaviour inChironomus anthracinusZetterstedt (Diptera: Chironomidae), one of the most ubiquitous species in cold‐temperate lakes of Northern Europe, was investigated in Lough Neagh, Northern Ireland. Aerial swarming is an indispensable part of mating in this species. It has been recognized that adults, emerging from offshore, travel to inshore resting sites for physical/sexual maturation, before gathering at lake margins to form swarms. After copulation, females immediately travel back to open‐water sites (up to 1000m offshore—the longest oviposition flight recorded for a chironomid species) for oviposition. Protandry was evident and sex ratios were completely reversed in the near‐shore swarming site and the offshore oviposition site. A sequence of mating behaviour was clarified, involving an initial grasp, landing, an end‐to‐end position, and separation. There was a high incidence of homosexual (male‐male) grasps, indicating that grasping is initiated with a fairly crude cue, and many (heterosexual) grasps failed to proceed to a correct mating position. This resulted in an estimation of only one out of eight grasps resulting in a proper copulation. More egg masses were found in the surface water farther offshore, together with spent females. An egg mass containedc.1000 eggs and hatching occurred within one month of oviposition.Sexual differences in the pattern of reproductive migration between the emergence/oviposition site offshore, the inland resting site, and the near‐shore swarming site, and the modes of mating and mating success achieved, together point to a possibility that the conspicuous swarming behaviour in this species may have evolved primarily through mate selection on the part of females. A swarm occurring at the end of the males’ lives serves as an efficient mechanism for females to select the best‐quality mate, while males have no other strategy than to participate vigorously in a swarm if they are to attain a reproductive success with choosy females. Thus, two sexes apparently adopt different strategies in their reproductive life: males spend their energy in swarming, while females pass through the swarm site with a quick but guaranteed reward and spend their remaining energy in reaching offshore sites with muddy substrata which provide the best chance of surviva

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05488.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Seven measurements were taken from 72 adult and yearling spruce grouseDendragapus canadensishens collected over a 10‐year period from north‐eastern Ontario, Canada. A principal components analysis (PCA) indicated keel ridge length, keel total length, and femur length, these being the most representative measurements of general body size. Skeletal mass, caecal length, wing length, and foot length had lower character loadings on the first principal component axis (PC1), suggesting they are unreliable measurements of body size. Measurements taken from bones (i.e. keel, femur) were more representative of general body size than external morphometric measurements (e.g. wing and foot length) which ornithologists traditionally use to estimate body size. Pre‐laying adults were the smallest individuals and pre‐laying yearlings the largest in the population studied. A discriminant functions analysis (DFA) of the seven measurements, with separated body mass as an eighth variable, demonstrated distinct separation between pre‐laying and post‐laying groups of birds on the basis of separated body mass. Keel ridge length was further implicated as an effective variable in the discrimination of birds from different la

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05489.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The mole‐rat (Spalax ehrenbergi) is a solitary, subterranean rodent that excavates and inhabits its own tunnel system. The present study employed continuous radio‐telemetry in order to determine the structure and use of the mole‐rat's territory throughout the year. The use of radiotagged animals revealed that the spatial division of individuals in one area cannot be predicted simply on the basis of the above‐ground distribution of mounds. It was shown that mole‐rat territories undergo constant change in use and location throughout the year, with tunnel lengths averaging 18.7 ± 4.0 m in the dry season and 39.1 ± 7.1 m in the rainy season. The basic pattern of the mole‐rat tunnel system consisted of a main tunnel, 20–40 cm below the ground, with several short secondary tunnels branching off it. Most of the nests were connected to the tunnel system by two or more exits. During one 24‐h period, a mole‐rat travelled about 17 times the total length of its territory. Mole‐rats are active for about 50% of the time all year round, mainly during the day, and always return to the same nest for resting periods. The mole‐rat traverses its territory by walking short distances (c.2 m) interspersed with pauses at certain permanent sites. While the pattern of territorial patrol normally remains uniform, under threat the patrol ceases to be homogeneous and the frequency of visits to confrontational areas increases. At these locations, the mole‐rat produces its‘head drumming’(vibrational) communication in order to announce its pres

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05490.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Growth rate and fledging success were assessed in natural and manipulated broods of the pallid swiftApus pallidus.Daily measurements of chick mass, wing length, and insect abundance allowed us to examine the short‐term variation of chick growth in relation to food availability.The number of fledged nestlings increased with brood size. Wing length and body mass were slightly but significantly smaller in larger broods, and the nestlings of enlarged broods needed longer to fledge. We discuss how these differences could influence survival after fledging.Hatching asynchrony caused a significant difference in growth among siblings, and the difference between the oldest and youngest chick was greater in larger broods.Chick growth was independent of daily food availability. We suggest that this was due to an increased effort of the parents at their expense, when food availability was poor.The ability of this species to raise an additional chick is in line with most findings on birds, but partially in contrast with results for the common swift in which, at least during poor seasons, the additional nestling caused an increased mortality and lowered the reproductive succes

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05491.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY