摘要:

Anthecological relations between a long‐spurred angraecoid orchid and pollinating Sphingidae are documented for the first time. In a primary forest on the Central Plateau of MadagascarAngraecum arachnitesSchltr. was found to be pollinated by and adapted to a single species of hawk‐moth,Panogena lingens(Butler), despite abundance of many concurrent Sphingidae of which several were also long‐tongued. Furthermore,P. lingenswas dimorphic in the length and breadth of its proboscis and only the morph with the longest and most slender proboscis was recorded to pollinateA. arachnites. Exclusive and precise adaptation to the latter morph ofP. lingensexisted in floral morphology and probably in other characteristics such as flowering phenology and chemical signalling. Several concurrently flowering orchid species were sharingP. lingensas a pollinator resource. The monophily inA. arachnitesis interpreted as a result of a refined long‐term specialization developed within an archaic evolutionary relationship in a relatively stable environment. The extraordinary number and diversity of long‐spurred Orchidaceae in Madagascar appears to be a direct coevolutionary consequence of an Old‐World‐unique diversity of long‐tongued archaic Sphingidae that has persisted in thi

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1985.tb01549.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

In laboratory feeding choice experiments several species of insects and molluscs eat acyanogenicLotus corniculatusleaves or petals in preference to cyanogenic alternatives. These species can be characterized as generalist feeders for whichL. corniculatusforms only an occasional dietary item for any particular individual. Some of the insects that were found to display selective eating were maintained on exclusive diets of either cyanogenic or acyanogenicL. corniculatus. Survival times varied considerably between species, but there was no evidence that mortalities were higher amongst the groups exposed to cyanide. These results suggest that the major role of cyanogenesis may be as a feeding inhibitor, not as a toxin.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1985.tb01550.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The zonation of 15 species ofLittorariain thescabragroup is described, using a transect method, at 13 mangrove localities in Australia, Thailand, Malaysia and Hawaii. At these localities the littorinids occurred only on trees, and showed both vertical and horizontal patterns of zonation, with broad overlaps between co‐occurring species. It is suggested that vertical distribution is determined mainly by behavioural responses, while the landward limits of horizontal distribution may be set by physiological tolerance. Several species occurred predominantly on either leaf or bark substrates, but no consistent associations with tree species were found. On the basis of local distribution patterns,Littorariaspecies can be classified as continental or oceanic in character. Oceanic species may be less tolerant of sediment in the water or on the substrat

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1985.tb01551.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Figs and their pollinating fig wasps are dependent on one another for propagation of their own kinds. The wasps reproduce by ovipositing through the styles of female flowers within the closed fig receptacles (syconia). About half of the female flowers within the syconia of monoecious figs have styles which are longer than the ovipositors of the wasp, and they will therefore produce seeds rather than wasp larvae. Since a longer ovipositor would enable a wasp to reach more ovules and deposit more eggs, the question arises at to why longer ovipositors have not evolved.In an attempt to answer this question, four seemingly plausible hypotheses are examined but each is shown to be problematical in some way. Consideration is then given to a fifth hypothesis which proposes that ovipositor length is constrained by abortion of syconia with relatively few seed embryos and many agaonid larvae. It is argued first that this pattern of abortion will be selected during a sustained period of heavy wasp infestation because seeds will then become scarce relative to pollen‐carrying wasps. Increased expenditure by the fig on seed production would therefore be favoured by natural selection. A greater expenditure on seeds would occur if young syconia with exceptionally heavy wasp infestations were dropped and the saved nutrients invested in syconia of a subsequent crop containing average levels of wasp larvae and seeds. Provided that the energy and nutrient cost of dropping young syconia is small, the selective advantage to the wasp of longer ovipositors is eliminated in this way. A stable coexistence of figs and wasps is therefore possible. The paper concludes by discussing two general predictions of the abortion hypothesis, and how these may be teste

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1985.tb01552.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The morphological variation of adultParochlus steinenii(Gerke) is described from measurements of two populations from the South Shetland Islands. Morphologically, the population from Ardley Island is significantly larger than the population from Livingston Island, and in both populations variation in forefemur length is generally greater than variation in either antennal or wing length. The final instar larvaof P. steineniiis described in detail. A consideration of the species' distribution in three geographically isolated areas, as well as of the greater morphological variation in polar as opposed to temperate populations, indicates that a flexible life history strategy in the larval stage may be important for survival in extreme environments.

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1985.tb01553.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0024-4066    

DOI:10.1111/j.1095-8312.1985.tb01549a.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY