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Peter M. Sherman

Bio: Peter M. Sherman is an academic researcher from University of Michigan. The author has contributed to research in topics: Gecarcinus quadratus & Gecarcinidae. The author has an hindex of 3, co-authored 3 publications receiving 256 citations.

Papers
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Journal ArticleDOI
TL;DR: Nightly variations in web dimensions suggest that hungry spiders invest more effort into foraging, while sated spiders re-allocate energy from continued foraging to egg production, and lend support to a seldom-tested tenet of optimal foraging theory: the direct relationship between foraging success and enhanced reproductive fitness.

180 citations

Journal ArticleDOI
TL;DR: Together, data from transects and experiments suggest that G. quadratus influences plant community composition and reduces seedling density and diversity in Costa Rica's Corcovado National Park through selective seedling consumption.
Abstract: The land crab, Gecarcinus quadratus (Gecarcinidae), affects plant diversity in a mainland, neotropical rain forest through selective seedling con- sumption. In Costa Rica's Corcovado National Park, G. quadratus lives infossorial populations with up to six crabs m −2 in coastal forest extending c. 600 m inland from the Pacific Ocean. A narrow transition zone (c. 30 m) separates the crab zone from the crabless zone that comprises the remainder of the 55 000-ha park. The composition of dicotyledonous plants from the adjacent zones were distinct: crab- less zone transects (240 m 2 ) contained 97 species representing 76 genera and 41 families; crab zone transects contained 46 species representing 38 genera and 25 families. Despite the narrow zonal separation, the crabless zone shared only 27.4, 29.9 and 52.8% of its species, genera and families, respectively, with the crab zone; in contrast, crab zone transects shared 56.5, 60.5 and 88% of their species, genera and families with the crabless zone. This abrupt diversity gradient suggests a powerful selection pressure in the crab zone preventing the establishment of cer- tain dicotyledonous species. Two years of experimental crab exclusion suggested that G. quadratus reduces seedling density and diversity. Densities of seedlings (3- 25 cm tall) within exclosures increased 144% over baseline values while control densities decreased. In contrast, seedlings at the cotyledon stage and taller (26- 50 cm) were unaffected by crab exclusion. Preference tests conducted in the crab zone revealed a five-fold ratio of mortality rates for seedlings transplanted from the crabless zone and crab zone respectively. However, when protected from crabs, transplanted crabless and crab zone seedlings survived similarly well over 6 mo (83 and 70% respectively). Together, data from transects and experiments suggest that G. quadratus influences plant community composition.

60 citations

Journal ArticleDOI
TL;DR: The effect of the fossorial land crab Gecarcinus quadratus on patterns of accumulation and distribution of leaf litter was studied for two years in the coastal primary forests of Costa Rica's Corcovado National Park and suggested that leaf choice by crabs may be species-specific.
Abstract: The effect of the fossorial land crab Gecarcinus quadratus (Gecarcinidae) on patterns of accumulation and distribution of leaf litter was studied for two years in the coastal primary forests of Costa Rica's Corcovado National Park. Within this mainland forest, G. quadratus achieve densities up to 6 crabs/m2 in populations extending along the Park's Pacific coastline and inland for ca 600 m. Crabs selectively forage for fallen leaf litter and relocate what they collect to burrow chambers that extend from 15 to 150 cm deep (N = 44), averaging (±SE) 48.9 ± 3.0 cm. Preference trials suggested that leaf choice by crabs may be species-specific. Excavated crab burrows revealed maximum leaf collections of 11.75 g dry mass—2.5 times more leaf litter than collected by square-meter leaf fall traps over several seven-day sampling periods. Additionally, experimental crab exclosures (25 m2) were established using a repeated measures randomized block design to test for changes in leaf litter as a function of re...

24 citations


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Book
01 Jan 2005
TL;DR: This work has shown clear trends in the dispersal and regeneration of seeds in disturbed areas, and these trends are likely to continue into the next decade.
Abstract: What determines the number and size of the seeds produced by a plant? How often should it reproduce them? How often should a plant produce them? Why and how are seeds dispersed, and what are the implications for the diversity and composition of vegetation? These are just some of the questions tackled in this wide-ranging review of the role of seeds in the ecology of plants. The authors bring together information on the ecological aspects of seed biology, starting with a consideration of reproductive strategies in seed plants and progressing through the life cycle, covering seed maturation, dispersal, storage in the soil, dormancy, germination, seedling establishment, and regeneration in the field. The text encompasses a wide range of concepts of general relevance to plant ecology, reflecting the central role that the study of seed ecology has played in elucidating many fundamental aspects of plant community function.

1,382 citations

Journal ArticleDOI
TL;DR: The Ocypodidae have now been shown to have the same role as Sesarmidae in terms of retention of forest products and organic matter processing in New world mangroves and it seems likely that ants have positive effects on mangrove performance.

401 citations

Book ChapterDOI
01 Jan 2005

194 citations

Journal ArticleDOI
TL;DR: The results indicate that invasive plants that change the architecture of native vegetation can substantially impact native food webs via nontraditional plant → predator →-consumer linkages.
Abstract: As primary producers, plants are known to influence higher trophic interactions by initiating food chains. However, as architects, plants may bypass consum- ers to directly affect predators with important but underappreciated trophic ramifications. Invasion of western North American grasslands by the perennial forb, spot- ted knapweed (Centaurea maculosa), has fundamentally altered the architecture of native grassland vegetation. Here, I use long-term monitoring, observational studies, and field experiments to document how changes in vegetation archi- tecture have affected native web spider populations and predation rates. Native spiders that use vegetation as web substrates were collectively 38 times more abundant in C. maculosa-invaded grasslands than in uninvaded grass- lands. This increase in spider abundance was accompanied by a large shift in web spider community structure, driven primarily by the strong response of Dictyna spiders to C. maculosa invasion. Dictyna densities were 46-74 times higher in C. maculosa-invaded than native grasslands, a pattern that persisted over 6 years of monitoring. C. mac- ulosa also altered Dictyna web building behavior and foraging success. Dictyna webs on C. maculosa were 2.9- 4.0 times larger and generated 2.0-2.3 times higher total prey captures than webs on Achillea millefolium, their primary native substrate. Dictyna webs on C. maculosa also captured 4.2 times more large prey items, which are crucial for reproduction. As a result, Dictyna were nearly twice as likely to reproduce on C. maculosa substrates compared to native substrates. The overall outcome of C. maculosa invasion and its transformative effects on vegetation archi- tecture on Dictyna density and web building behavior were to increase Dictyna predation on invertebrate prey C89 fold. These results indicate that invasive plants that change the architecture of native vegetation can substantially impact native food webs via nontraditional plant ? preda- tor ? consumer linkages.

145 citations

Journal ArticleDOI
TL;DR: Evidence is provided that the behaviour of trap‐building predators is not stereotypic or fixed as was once commonly accepted, rather it can vary greatly, depending on the individual's internal state and its interactions with external environmental factors.
Abstract: Foraging theory was first developed to predict the behaviour of widely-foraging animals that actively search for prey. Although the behaviour of sit-and-wait predators often follows predictions derived from foraging theory, the similarity between these two distinct groups of predators is not always obvious. In this review, we compare foraging activities of trap-building predators (mainly pit-building antlions and web-building spiders), a specific group of sit-and-wait predators that construct traps as a foraging device, with those of widely-foraging predators. We refer to modifications of the trap characteristics as analogous to changes in foraging intensity. Our review illustrates that the responses of trap-building and widely-foraging predators to different internal and external factors, such as hunger level, conspecific density and predation threat are quite similar, calling for additional studies of foraging theory using trap-building predators. In each chapter of this review, we summarize the response of trap-building predators to a different factor, while contrasting it with the equivalent response characterizing widely-foraging predators. We provide here evidence that the behaviour of trap-building predators is not stereotypic or fixed as was once commonly accepted, rather it can vary greatly, depending on the individual's internal state and its interactions with external environmental factors.

143 citations