Alternative Reproductive Tactics in Spiders

The comparative study of reproduction at the level of populationand individual is a relatively recent development in spiderresearch. Such study is necessary to describe and examine alternativereproductive tactics. Female spider tactics are related to adaptationsfor a carnivorous mode of feeding. Being the larger of the sexes,the female has the alternative of mating with or preying uponattending males. In web building spiders, which are generallysolitary, other female alternatives are related to characteristicsof a web used in prey capture. These alternatives include differentresponses when defending the web, and individually buildingthe web so that it does or does not contact another. Tacticsmay vary in communal species which build a sheet-like structure,as females may remain in the colony or emigrate and establisha small web. Male spiders usually search for females, and matingoccurs on or near a female retreat or web. A male may show differentalternatives in mate searching, demonstrate various courtshipand copulatory tactics, copulate or feed on the female's preywhile she feeds, and guard the female after mating or departand search for another female. Certain characteristics of femalesare related to these male alternatives, these characteristicsbeing: larger size and longer life expectancy as compared withthe male, carnivorous feeding, and sexual receptivity. Maleweb spiders may also use alternatives while defending positionon the female web. These alternatives are related to the designand placement of the web, and occasional web abandonment bythe female. Relevant literature is reviewed and research suggested.     

Winter climate change implications for decomposition in northeastern forests: comparisons of sugar maple litter with herbivore fecal inputs

Forests in northeastern North America are influenced by varying climatic and biotic factors; however, there is concern that rapid changes in these factors may lead to important changes in ecosystem processes such as decomposition. Climate change (especially warming) is predicted to increase rates of decomposition in northern latitudes. Warming in winter may result in complex effects including decreased levels of snow cover and an increased incidence of soil freezing that will effect decomposition. Along with these changes in climate, moose densities have also been increasing in this region, likely affecting nutrient dynamics. We measured decomposition and N release from ¹⁵N‐labeled sugar maple leaf litter and moose feces over 20 months in reference and snow removal treatment (to induce soil freezing) plots in two separate experiments at the Hubbard Brook Experimental Forest in New Hampshire, USA. Snow removal/soil freezing decreased decomposition of maple litter, but stimulated N transfer to soil and microbial biomass. Feces decomposed more rapidly than maple litter, and feces N moved into the mineral soil more than N derived from litter, likely due to the lower C : N ratio of feces. Feces decomposition was not affected by the snow removal treatment. Total microbial biomass (measured as microbial N and C) was not significantly affected by the treatments in either the litter or feces plots. These results suggest that increases in soil freezing and/or large herbivore populations, increase the transfer rate of N from plant detritus or digested plants into the mineral soil. Such changes suggest that altering the spatial and temporal patterns of soil freezing and moose density have important implications for ecosystem N cycling.     

Natural history of the non-solitary sheetweaving spider Anelosimus jucundus (Araneae: Theridiidae)

Field observations were made on one Panamanian population of Anelosimus jucundus. Almost all webs were found in a relatively exposed area, on small shrubs and composites. This is in contrast to A. eximius , a colonial congeneric which in our study site built its large webs along moist, fern-covered banks. Web structure varied with different plant substrates; for example, only some of the webs incorporated a clearly defined lower sheet. Webs were built by penultimate instar females, and perhaps by adult females and males. In some cases, several adult females inhabited a web, but they remained under separate leaf canopies; during census observations co-operative efforts were not noted. Prey consisted mainly of winged insects. Juvenile sex ratio was about equal. The degree of sociality demonstrated by A. jucundus is discussed.