摘要:

In climatically seasonal habitats, favourable periods for reproduction may be simply determined by large annual changes in temperature or rainfall. In contrast, in climatically less seasonal habitats, reproductive timing may be determined by a wide variety of seasonal factors. Three hypotheses regarding reproductive timing were tested for a fruit bat, Huplonycteris Jischeri Lawrence, by comparing reproductive timing and climate at four moderately seasonal Philippine sites with differing climates. Bats were sampled in five years on Negros Island (9″22′N, 123″l I'E), and in one to four months on four other islands. Flower and fruit abundance was monitored in two years on Negros. In five years on Negros, parturition and lactation coincided with the time of the average dry‐wet season transition and early wct season, but did not vary in response to substantial annual variation in the onset of rains. Reproductive timing did not change in response to annual variations in Rower or fruit abundance; lactation coincided with a peak in fruit abundance in one year, but not in a second, and reproductive success appeared to be reduced when lactation coincided with scarce resources. At a second site with a different pattern of rainfall, reproduction was nevertheless synchronous with Negros. Samples from two of the three remaining localities indicate a two‐ to three‐month lag in reproductive events relative to Negros, despite rainfall patterns remarkably similar to that of Negros. All three hypotheses for reproductive timing were rejected. As an alternative, Huplonycteris may evolve timing patterns in response to local seasonal patterns of resource abundance.Huplonycteris has an eight‐month post‐implantation delay 'in embryonic development. Six hypotheses on the adaptive significance of this delay in Huplonyrferis were evaluated. Three were rejected, but the data were consistent with the remaining hypotheses: (1) The delay sets the time of parturition at a particular time of year; (2) the delay allows all females to produce young relatively synchronously; and (3) the delay allows females to resorb or abort defective embryos without losing an opportunity f

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02396.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Biased sex ratios of breeding threespine sticklebacks (Gasterosteus aculeatus L.) occur naturally in tide‐pools of a Quibec saltmarsh. We experimentally manipulated sex ratios in certain pools to evaluate the effects on male behaviour and reproductive success (RS). Sticklebacks were stocked at male: female ratios of 1: I, 1: 2 and 2: 1 and observed for a 23‐day inter‐tidal period. In male‐biased pools, only half of the males built nests, compared to nearly 100% in unbiased and female‐biased pools. Males in male‐biased pools also were less likely to rebuild after losing a nest, visited their nests less often, were more likely to abandon or destroy their nests, had lower RS (measured as the proportion of males hatching fry), but hatched fry sooner, than males in other pools. In female‐biased pools, males built nests sooner, lost more nests due to nest‐raiding by females, spent more time in aggression (proportion of time spent fighting and threatening), spent more time attacking female conspecifics than male conspecifics or heterospecifics, and courted more frequently, than males in other pools. Habituation to conspecific males, but not to females, occurred in all pools. These findings are discussed with respect to sexual s

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02397.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02398.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Subfossil bones of the extinct New Zealand duck, Euryanas finschi (Van Beneden), from late Otiran glacial‐early Holocene (20,000‐ 1 1,000 years BP) and late Holocene (2,000‐1,000 years BP) deposits were compared. Ten percent reduction in wing bone lengths and reductions in other pectoral girdle elements suggest reduced flight ability and may be related to possible ecological changes such as relaxation of predation pressure and increase in stability of food supply. Comparisons of Euryanas with extant members of the Anus aucklandica (Gray) species complex indicate that in the late Holocene Euryanas had similar flight ability to A. aucklandica chlorotis Gray,

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02399.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The ratio of the medulla to the cortex (M/C ratio) was determined for three species of Megachiroptera, and the ratio of the inner medulla to the cortex (IM/C ratio) was determined for 28 species of insect‐eating Microchiroptera from diverse savanna and montane habitats within Malawi. Although all these species occur in the southern savanna biotic zone of Africa, each varies in its ability to exploit the African rainforest, arid and desert biotic zones. The kidneys of the Megachiroptera were very different to those of the insect‐eating Microchiroptera, and these differences were related to the need of fruit‐bats to excrete the surplus water associated with their diet. The urine concentrating capacity of each species of Microchiroptera was predicted from the IM/C ratio. Family characteristics were examined, and the urine concentrating capacities of the Malawian bats were compared with bats from elsewhere, and with some rodents. The insect‐ eating Microchiroptera exemplified a very diverse range of IM/C ratios. The IM/C ratio of each species was compared with its drinking behaviour in captivity, diet, foraging strategy, flight, aspect ratio, domicile, roosting behaviour and habitat. It was hypothesized that the ability of insect‐eating Microchiroptera to conserve urinary water would be an advantage to species: (a) living in xeric habitats; (b) adapted for sustained high‐speed flight; (c) roosting in hot dry domiciles; (d) roosting in solitude; and (e) living at high altitudes where seasonal low temperatures induce torpidity. These hypotheses were tested, and it was concluded that, while the ability to conserve urinary water may have been an advantage in most of these situations, it was no

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02400.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

A new species of Pterolebias from Caceres, Paraguay River Basin, State of Mato Grosso, Brazil, is described. It was found in a temporary lagoon on the Brazilian Central Cerrado and seems to have the same annual habits of the other species of the group. The new species differs from all other species but P. staeckiin the colour pattern on the sides of the body, which consists of longitudinal stripes. From P. siaecki it differs in the relative length of the pelvic‐fin and of the predorsal area and by the number of scales in the longitudinal series. The similarity between P. bokermanni and P. longipinnis is discusse

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02401.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Chela morphology and muscle stress were compared between temperate and tropical populations of stone crabs Menippe mercenuriu (Say) to test whether environmental differences might result in greater crushing strength in the tropics. Such differences include increased crab diversity in the tropics (which might lead to greater fighting among congeners), increased prey exoskeleton calcification in the tropics, and year round chela use in the tropics as opposed to seasonal chela use in the temperate population.No latitudinal differences were found in any aspect of chela morphology, including relative chela size, mechanical advantage, apodeme surface area, and angle of muscle fibre pinnation. Summer measurements of crusher chela muscle stress were also similar between the two populations.The maximum muscle stress determined for M. mercenariu was 220 N ∼r n ‐∼, much higher than stress levels previously reported for crustaceans. Other researchers have typically measured forces either from autotomized chelae or by measuring forces required to open a closed chelae. I have determined muscle stress using a force transducer that measures active gripping strength in live

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02402.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Sperm morphology was studied in 10 species of the caviomorph rodent Ctenomys. Ctenomys argentinus, C. conoueri, C. dorbigny and C.perrensis had symmetric spermatozoa with paddle‐like heads. Ctenomys australis, C. mendocinus, C. porteousi, C. rionegrensis and Ctenomys sp., on the other hand, had spermatozoa with paddle‐like heads but with the tail inserted at one side of the central axis and a nuclear caudal extension originating from the base of the head at the opposite side of the insertion of the tail and running parallel to the flagellum; these spermatozoa are referred to as simple‐asymmetric. In C. yolandae, a complex‐asymmetric morphological type not previously described for the genus was found. This type is characterized by the presence of two nuclear caudal extensions. Symmetric spermatozoa (total length = 52 pm) were shorter than asymmetric (both simple and complex) ones (total length = 87 pm). In spite of these differences, the relative size of heads, midpieces and tails were maintained in the three groups, representing 12%, I I YO and 88% of the average total length, respectively. Within each group of species bearing the same sperm type, a low interspecific variability both in morphological patterns and dimensions of sperm cells was observed. This low interspecific variability associated with the north to south geographical distribution of species having, respectively, symmetric and asymmetric spermatozoa, suggests that these characters appeared at an early stage in evolution of the group, and probably played an important role in the first steps of speciation by promoting reproductive is

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02403.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02404.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Female‐biased sex ratios are often associated with small, isolated populations. These conditions are exhibited in populations of Platyarthrus hoflmannseggi (Brandt, 1833), a small, blind woodlouse which lives almost solely in ant nests. This study was undertaken to determine how sex ratio varies with population size in P. hoffmunnseggi and how both of these factors affect population growth rate. To accomplish this, a total of 2155 of these isopods were collected from 20 nests of the ant LusiusJaour (Fabricius, 1781). The majority of the isopod populations were female‐biased. The behaviour and survivorship of the isopods in their own and foreign antcolonies were compared and suggest that the free movement of P. hoffmannseggi individuals among ant colonies may be extremely limited. These studies also show how isopods are nutritionally linked to their hosts. Measurement of the woodlice revealed two distinct size/age classes in each population and allowed the change in sex ratio from one generation to the next to be estimated. Female‐biased populations produce in future generations relatively more females and fewer males than populations of a similar size with a sex ratio of unity. There was no correlation between the degree of female bias and the rate of population growth. These findings are reviewed in the light of recent theoretical sex ratio models and the possible control of the isopods sex allocation by unusual chromosomal mechanisms and intracellular para

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02405.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY