The interaction of soil biota and soil structure under global change

The structural framework of soil mediates all soil processes, at all relevant scales. The spatio-temporal heterogeneity prevalent in most soils underpins the majority of biological diversity in soil, providing refuge sites for prey against predator, flow paths for biota to move, or be moved, and localized pools of substrate for biota to multiply. Just as importantly, soil biota play a crucial role in mediating soil structure: bacteria and fungi aggregate and stabilize structure at small scales (μm–cm) and earthworms and termites stabilize and create larger-scale structures (mm–m). The stability of this two-way interaction of structure and biota relations is crucial to the sustainability of the ecosystem. Soil is constantly reacting to changes in microclimates, and many of the soil–plant–microbe processes rely on the functioning of subtle chemical and physical gradients. The effect of global change on soil structure–biota interactions may be significant, through alterations in precipitation, temperature events, or land-use. Nonetheless, because of the complexity and the ubiquitous heterogeneity of these interactions, it is difficult to extrapolate from general qualitative predictions of the effects of perturbations to specific reactions. This paper reviews some of the main soil structure–biota interactions, particularly focusing on soil stability, and the role of biota mediating soil structures. The effect of alterations in climate and land-use on these interactions is investigated. Several case studies of the effect of land-use change are presented.     

Population genetics of Dioon edule Lindl. (Zamiaceae, Cycadales): biogeographical and evolutionary implications

Dioon edule Lindl. (Zamiaceae) is a cycad endemic to Mexico, that occurs as one species D. edule and the geographical variety D. edule var. angustifolium (Miq.) Miq. Dioon edule has a north to south distribution in eastern Mexico. In this study, we analysed 14 allozymic loci in eight populations of D. edule from its total distribution range by sampling all known populations. Patterns of diversity and genetic variability, within and among populations, were obtained. The mean number of alleles per locus ( A ) was 1.44 and the percentage of polymorphic loci was relatively high ( P  = 54.78). The mean observed ( H _O ) and expected heterozygosity ( H _E ) were 0.27 and 0.24, respectively. F -statistics revealed an excess of heterozygous genotypes, locally and globally ( F  = −0.17 and f  = −0.27, respectively). The genetic variation explained by differences among populations was only 7.5%. We also detected a negative relationship between genetic diversity and latitude. On average, the gene flow between population pairs was relatively high ( Nm  = 2.98); furthermore, gene flow between population pairs was significantly correlated with geographical distances ( r  = −0.38, P  = 0.025). Therefore, patterns of genetic diversity in D. edule appear to be associated with the post-Pleistocene spread of the species, from its southerly (origin) to its northerly range (derived populations, including its central distribution). The biogeographical and evolutionary aspects of the results of this study are discussed. We recognize Dioon angustifolium Miq. for the northernmost disjunct populations.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80 , 457–467     

Craniological differentiation between European wildcats (Felis silvestris silvestris), African wildcats (F. s. lybica) and Asian wildcats (F. s. ornata): implications for their evolution and conservation

Intraspecific diversification of the wildcat (Felis silvestris), including the European wildcat (F. s. silvestris), the Asian wildcat (F. s. ornata) and the African wildcat (F. s. lybica), was examined based on 39 cranial morphology variables. The samples of free‐ranging cats originated from Britain, Europe, Central Asia and southern Africa, consisting of both nominal wildcat specimens (referred to henceforth as ‘wildcats’) and nominal non‐wildcat specimens (‘non‐wildcats’) based on museum labels. The skull morphology of ‘wildcats’ from Britain and Europe is clearly different from that of ‘wildcats’ of Central Asia and southern Africa. The latter are characterized especially by their proportionately larger cheek teeth. On the basis of principal component, discriminant function and canonical variate analyses, the skull morphology of British ‘non‐wildcats’ is less distinct than is that of British ‘wildcats’ from the skull morphologies of ‘wildcats’ of Central Asia and southern Africa. On the other hand, the skull morphology of southern African ‘non‐wildcats’ is as distinct from those of ‘wildcats’ of Britain and Europe as is that of southern African ‘wildcats’. We suggest that the evolution of the modern wildcat probably consisted of at least three different distribution expansions punctuated by two differentiation events: the exodus from Europe during the late Pleistocene, coinciding with the emergence of the steppe wildcat lineage (phenotype of Asian–African wildcat), followed by its rapid range expansion in the Old World. The second differentiation event was the emergence of the domestic cat followed by its subsequent colonization of the entire world with human assistance. Considering the recent evolutionary history of, and morphological divergence in, the wildcat, preventing hybridization between the European wildcat and the domestic cat is a high conservation priority. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 83 , 47–63.     

Morphological and allozyme variation of Eidolon helvum (Mammalia: Megachiroptera) in the islands of the Gulf of Guinea

Morphological and genetic variation is evaluated among populations of the bat, Eidolon helvum , in the islands of the Gulf of Guinea (Central Africa). The populations from the islands of Bioko, Principe, and Sao Tome do not show significant phenetic differentiation, although a trend towards a reduction of size is found in the latter two islands. The low genetic distances between populations, as well as their values of Wright's fixation indexes, suggest that gene flow has hampered differentiation on these islands. In contrast, the population from Annobon, the smallest and farthermost island, shows remarkable morphological and genetic differentiation. On the mainland, E. helvum displays unique migratory and dispersal behaviours, but migratory behaviour was not found in any of the island populations. The combination of selective forces in harsher oceanic environments and restricted gene flow among populations appears to have favoured the high degree of morphological differentiation of E. helvum on Annobon. Due to the extended length of the dry season in Annobon, an earlier achievement of sexual maturity–and consequently smaller size—may be advantageous in the absence of migration. The differentiation is more marked among females, which also suggests that selection may be linked to the reproductive pattern. The population of the island of Annobon is herein described as a new subspecies, Eidolon helvum annobonensis subsp. nov.     

I Foresee My Life: The Ritual Performance of Autobiography in an Amazonian Community

I Foresee My Life: The Ritual Performance of Autobiography in an Amazonian Community . Suzanne Oakdale. Lincoln: University of Nebraska Press, 2006. 206 pp.     

Terrestrial versus aquatic phenotypes correlate with hydrological predictability of habitats in a semiterrestrial salamander (Urodela, Plethodontidae)

Terrestrial adaptations by small, desmognathine salamanders in Appalachian stream communities have been viewed as evolved responses to large, aquatic, predatory congeners. We tested the role of moisture in the development of adaptive phenotypes in the small, semiterrestrial Desmognathus ocoee . We measured indicators of relative terrestrial vs. aquatic phenotypes (i.e. tolerance of desiccation, anatomical depression of body/tail) using individuals from stream habitats having different flow regimes within each of three geographical locations. Salamanders from intermittent, first-order streams exhibited greater desiccation tolerance, took longer to reach tolerance limits, and had more anatomically depressed bodies/tails than those from second-order, perennial streams, regardless of location. Phenotypes of salamanders from second-order streams showed aquatic tendencies. Phenotypic variation was consistent with relative habitat stability and not with relative abundance of large congeners. MtDNA analysis revealed that individuals grouped together based on geographical location and not habitat type, implying that the observed phenotypic differences arose in situ at each geographical location. Recent phylogenetic reconstructions of the Desmognathus indicate that large, aquatic forms are derived, and their appearance corresponds with the late Cenozoic development of modern Appalachian topography. We propose that radiation of desmognathine lifestyles and associated phenotypes tracked the formation of moisture-stability gradients associated with the creation of cool, wet, montane habitats.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 227–238.     

Noncorrelated evolution between herbivore- and pollinator-linked features in Aristolochia chilensis (Aristolochiaceae)

The effect of mutualists (i.e. pollinators) and antagonists (i.e. herbivores) can have non-additive effects on plant fitness. This is often interpreted as evidence for correlated evolution on a suite of traits leading to an increase and decrease of the interaction of plants with mutualists and antagonists, respectively. This situation has been found to prevail in plants that have large floral and fruit displays but are not limited by pollinators for seed set. We suggest the alternative hypothesis, where plants limited by pollinators for seed set (e.g. deceit-pollinated plants) exhibit additive effects of pollinators and herbivores on fitness (i.e. noncorrelated evolution). Using a 2 × 2 factorial design, we tested this hypothesis by solely and simultaneously evaluating the effects of pollinators and the single herbivore, Battus polydamas archidamas , on female reproductive success of Aristolochia chilensis . Plants exposed to herbivores presented 2.6-fold greater herbivory than plants that excluded them. In addition, plants exposed to pollinators showed strong limitation by pollinators for seed set compared with other plants of the genus Aristolochia. However, only pollinators had a significant effect on fruit and seed set because plants that excluded them did not set fruits or seeds. Furthermore, herbivores and pollinators exerted additive effects on fruit and seed production. Collectively, these results indicate that herbivore- and pollinator-linked traits in A. chilensis exhibit noncorrelated evolution.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 239–245.     

Concentration and Enzyme Content of In Vitro-Cultured Babesia bigemina-Infected Erythrocytes1

ABSTRACT. Clones of in vitro-cultured Babesia bigemina-infected erythrocytes were concentrated by several density gradient procedures. The density range of infected erythrocytes containing pairs of parasites was 1.077 to 1.089 g/ml, whereas the density range of infected erythrocytes containing single parasites was 1.092 to 1.100 g/ml. Three enzymes-lactate dehydrogenase, glucose-phosphate isomerase, and glutamate dehydrogenase-were found associated with infected erythrocytes. The parasite-specific enzyme and/or isoenzymes were shown to have different mobility patterns in starch gel electrophoresis from those found in the normal bovine erythrocytes. The enzyme 6-phosphogluconate dehydrogenase was not detected as a parasite-specific enzyme in B. bigemina-infected erythrocytes.