Seasonal Variability in Abundance and Diversity of Soil Gymnamoebae Along a Short Transect in Southeastern USA

The abundance and diversity of gymnamoebae in three subsoils varying in compaction and water retention along a 1.2 m transect were documented as the local climatic conditions changed from late summer 1999 through mid-summer 2000. The mean density of gymnamoebae for the loose soil (1,655/g) was greater than either the most compact (1,468/g) or moderately compact soil (851/g). Minimum densities occurred in middle and late summer for all soils while significant (F = 38.803, < or = 0.0002) density peaks at 3.212/g occurred in early summer in the most compact soil, 2.928/g in the least compact, and 2,209/g in the moderately compact soil. Limax non-eruptive gymnamoebae (mt 2) correlated (r = 0.49, p < or = 0.016) with moisture while eruptive limax gymnamoebae ( 3) correlated with temperature (r = 0.07, p < or = 0.024), moisture (r = 0.58, p < or = 0.001) and precipitation (r = 0.46, p < or = 0.029). Flattened or discoid amoebae (mt 4) dominated throughout most of the survey, and the two limax groups showed inverse relationships. Chi-square analyses showed significant differences in the numbers of limax eruptive gymnamoebae compared to all other morphotypes on all but one sampling period.     

Convergence and parallelism among cicadas of Argentina and the southwestern United States (Hemiptera: Cicadoidea)

Cicadas of the genera Derotettix in Argentina and Okanagodes in the south-western United States resemble each other in colour, live on salt-tolerant plants ( Atriplex spp. etc.), nearly match the colour of their respective host plants and produce songs above the range of avian hearing. The Argentine cicadas are smaller, but have nearly identical thermal limits for activity measured by the minimum temperature for flight (20–24 °C) and a body temperature at heat torpor (48–49 °C). The species shift activity from basking sites to shade at temperatures above 37 °C, although O .  gracilis rises to a significantly higher temperature (40.7 °C) than its congener (38.2 °C) or Derotettix (37.2 °C). The thermal tolerances are the highest reported for cicada species. A third group using halophytes in Argentina ( Babras sonorivox ) has similar temperature tolerances and is cryptically coloured. The genera are convergent with respect to morphology, coloration, body size, behaviour, habitat choice and host plant selection. The similarities of thermal tolerances and their influence on behaviour can be viewed as parallelism because the underlying mechanisms are the same in all species studied.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 281–288.     

Testing models of female reproductive migratory behaviour and population structure in the Caribbean hawksbill turtle, Eretmochelys imbricata, with mtDNA sequences

Information on the reproductive behaviour and population structure of female hawksbill turtles, Eretmochelys imbricata , is necessary to define conservation priorities for this highly endangered species. Two hypotheses to explain female nest site choice, natal homing and social facilitation, were tested by analyzing mtDNA control region sequences of 103 individuals from seven nesting colonies in the Caribbean and western Atlantic. Under the social facilitation model, newly mature females follow older females to a nesting location, and subsequently use this site for future nesting. This model generates an expectation that female lineages will be homogenized among regional nesting colonies. Contrary to expectations of the social facilitation model, mtDNA lineages were highly structured among western Atlantic nesting colonies. These analyses identified at least 6 female breeding stocks in the Caribbean and western Atlantic and support a natal homing model for recruitment of breeding females. Reproductive populations are effectively isolated over ecological time scales, and recovery plans for this species should include protection at the level of individual nesting colonies.     

Growth and production of five species of Ephemeroptera larvae from an experimental recirculating stream

SUMMARY. The production and growth of the larvae of five species of Ephemeroptera in an experimental recirculating stream-channel are described. The most abundant species were Baetis rhodani , which achieved a maximum population density of c. 29,000 m^-2 in August, and Ephemerella ignita which reached a density of c. 13,000 m^-2 in the spring. Three other common speeies, Paraleptophlebia submarginata, Centroptilum luteolum and Caenis rivulorum were present at lower densities (< 1000 m^-2). B. rhodani had five cohorts in a year whilst C. luteolum had two or possibly three. E. ignita, C. rivulorum and P. submarginata were univoltine. Mean speeifie growth rates were calculated for each species, the maximum being 3.26±0.49% length day^-1 for E. ignita (3 April—15 May). Production of each of these five species of Ephemeroptera was calculated giving a total annual production of 10.2 g dry wt m^-2 (computational method).