摘要:

Caterpillars of the hawkmothEumorpha fasciataare highly polymorphic for colour, with green, pink, and pink‐and‐yellow forms in the second through fourth instars, and green and multicoloured forms in the fifth instar. Four years of field censuses on four foodplant species determined that all morphs were found on all plant species; morph frequencies were homogeneous on each plant species over time; and morph frequencies differed consistently among plant species. When larvae were reared from eggs on three of the hostplant species in the laboratory, differences in morph frequencies paralleled the census results. Thus foodplant quality is one factor affecting larval colour inE. fasciata.A literature survey reveals that foodplant effects on larval colouration may be widespread in the family Sphingidae, but most reports are anecdotal rather than experimental. The implications of this mechanism of colour determination are discus

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1995.tb01103.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Cranio‐dental characteristics are quantified between micro‐ and megachiropteran nectarivores and compared with microchiropteran animalivores, frugivores, and megachiropteran frugivores. Microchiropteran nectarivores share many characteristics with megachiropteran nectarivores and frugivores, but differ in having a long, narrow head. Megachiropterans have wide zygomata, which would allow for more jaw musculature. Diminutive cheekteeth are characteristic of nectarivory in both suborders, but both have relatively large canines. Teeth in nectarivores can occupy as little as a tenth of the palatal area compared to nearly two‐thirds in microchiropteran animalivores. The proportion that the dilambdodont stylar shelf occupies of molars in microchiropteran nectarivores can be as much as that in microchiropteran animalivores (insectivorous and carnivorous bats) or as little as that in microchiropteran frugivores but not as extreme as either. In addition to dimunitive teeth, nectarivores have fused mandibles and upper canines that are worn from contact with the lower canines (thegosis). These characteristics may be necessary for the lower jaw to support an elongated, mobile tongue. While microchiropteran nectarivory, frugivory, and carnivory probably evolved independently from an insectivorous microchiropteran ancestor, megachiropteran nectarivory probably evolved from megachiropteran frugivory or the re

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1995.tb01104.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Direct evidence of competition is seldom available from the fossil record. Overgrowth relationships of encrusting marine organisms constitute an exception but have previously been reported in only temporally and geographically local occurrences. Results of overgrowths between members of two bryozoan clades, the Cyclostomata and the Cheilostomata, have been compiled for faunas distributed through the past 100 Myr. The cheilostomes have consistendy out‐competed the cyclostomes, with approximately 66% overgrowdi success through the entire interval. This difference in success in direct interactions along with the Mid‐Cretaceous rapid radiation of cheilostomes is interpreted as a factor in the Mid‐ to Late Cretaceous reversal from the previous diversification to stasis or gradual decline of cyclostome dive

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1995.tb01105.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Inbreeding is said to reduce vigour and fitness. It may also determine how a population responds to selection. Local populations ofCallosobruchus maculatus, the cowpea seed beetle, are established annually from small numbers of founders and the species has been distributed to many parts of the world where isolated populations may have been founded by very small numbers of individuals. After more than 20 generations of inbreeding, inbred lines have been shown to diverge from a common ancestral stock in similar directions with respect of some variables such as developmental speed, but haphazardly in respect of other parameters such as male weight. The respective roles of drift and of selection as effective evolutionary forces in inbred lines are discussed in the light of these results. It is argued that some intraspecific differences inC. maculatusmay be explained as a product of periodic inbreeding, but that the process does not impair the ability to adapt to local conditions so contributing to the status of the species as a pest of international importance.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1995.tb01106.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY