Phylogeny of Hypselodoris (Nudibranchia: Chromodorididae) with a review of the monophyletic clade of Indo-Pacific species, including descriptions of twelve new species

This work provides an account of the systematics and phylogeny of Hypselodoris . Aspects of the morphology of 42 species are described and the systematic status of an additional 11 species is discussed. Twelve new species are described: Hypselodoris alboterminata, H. bertschi, H. bollandi, H. fucata, H. iacula, H. insulana, H. krakatoa, H. paulinae, H. reidi, H. rudmani, H. violabranchia and H. zephyra. A phylogenetic analysis supports the monophyly of Hypselodoris and Risbecia . Two distinct clades of Hypselodoris are present. One contains species from the Atlantic and eastern Pacific while the other contains species limited to the Indo-Pacific tropics and adjacent temperate regions. Species from the Atlantic and eastern Pacific are bluish in body colour and have a plesiomorphically large receptaculum seminis while Indo-Pacific taxa are variably coloured and all have a minute receptaculum seminis. The distribution and size of mantle glands provides a wealth of morphological characters. With few exceptions, mantle glands vary in closely related species and are important for distinguishing members of smaller clades. Mantle gland distribution is therefore useful in identifying preserved material that is difficult to identify to species in the absence of the pigment of living specimens. Similar colour patterns found in sympatric species of Hypselodoris appear to be a result of both common descent and convergence between less closely related lineages. Biogeographic distributions of sister taxa provide several examples of vicariance. Examination of these cases shows that no single vicariant pattern is present, but vicariance appears to occur at the margins of the Indo-Pacific rather than centrally. Some vicariance occurs even within archipelagos such as the Hawaiian Islands. These cases largely refute the generality of the hypothesis of Springer (1982), that Pacific Plate and Australasian Plate endemic sister taxa should predominate.     

Interannual variability in carbon dioxide fluxes and flux–climate relationships on grazed and ungrazed northern mixed-grass prairie

The annual carbon (C) budget of grasslands is highly dynamic, dependent on grazing history and on effects of interannual variability (IAV) in climate on carbon dioxide (CO₂) fluxes. Variability in climatic drivers may directly affect fluxes, but also may indirectly affect fluxes by altering the response of the biota to the environment, an effect termed ‘functional change’. We measured net ecosystem exchange of CO₂ (NEE) and its diurnal components, daytime ecosystem CO₂ exchange (P_D) and night‐time respiration (R_E), on grazed and ungrazed mixed‐grass prairie in North Dakota, USA, for five growing seasons. Our primary objective was to determine how climatic anomalies influence variability in CO₂ exchange. We used regression analysis to distinguish direct effects of IAV in climate on fluxes from functional change. Functional change was quantified as the improvement in regression on fitting a model in which slopes of flux–climate relationships vary among years rather than remain invariant. Functional change and direct effects of climatic variation together explained about 20% of variance in weekly means of NEE, P_D, and R_E. Functional change accounted for more than twice the variance in fluxes of direct effects of climatic variability. Grazing did not consistently influence the contribution of functional change to flux variability, but altered which environmental variable best explained year‐to‐year differences in flux–climate slopes, reduced IAV in seasonal means of fluxes, lessened the strength of flux–climate correlations, and increased NEE by reducing R_E relatively more than P_D. Most of these trends are consistent with the interpretation that grazing reduced the influence of plants on ecosystem fluxes. Because relationships between weekly values of fluxes and climatic regulators changed annually, year‐to‐year differences in the C balance of these ecosystems cannot be predicted from knowledge of IAV in climate alone.     

Mitochondrial DNA and two perspectives on evolutionary genetics

This essay reviews comparative studies of animal mitochondrial DNA (mtDNA), with emphasis on findings made and ideas developed at Berkeley. It argues that such studies are bringing together two previous paths of progress in evolutionary biology. One path is that of those who worked far above the species level and were concerned with genealogical trees, time scales and the accumulation of new mutations on surviving molecular lineages. The other path is that of those who worked at and below the species level and were concerned mainly with population structure, migration and the frequencies of alleles that existed in an ancestral population. This fusion of paths is made possible by the high rate at which mutations accumulate on mtDNA lineages and by this molecule's uniparental and apparently haploid mode of inheritance. These properties make mtDNA a superb tool for building trees and time scales relating molecular lineages at and below the species level. In addition, owing to its mode of inheritance, mtDNA is more sensitive to bottlenecks in population size and to population subdivision than are nuclear genes. Joint comparative studies of both mtDNA and nuclear DNA variability give us valuable insights into how effective population size has varied through time. Such studies also give insight into the conditions under which mtDNA from one species can colonize another species.     

Microbial diversity in soil: effect of releasing genetically engineered micro-organisms

This review examines the potential for change in microbial diversity, with the emphasis on bacteria, in soil resulting from the introduction of genetically engineered microorganisms (GEMs). With the advent of GEMs came the impetus for new technologies to recover these micro-organisms from soil and to assess their effects on microbial diversity. This review also presents general aspects of and genetic approaches to accessing bacterial diversity in the environment.     

Timing is everything? Phenological synchrony and population variability in leaf‐chewing herbivores of Quercus

Abstract.  1. Specialization on ephemeral resources (e.g. new leaves) should produce large annual variation in herbivore population size when the timing of availability of those resources is unpredictable. Despite considerable evidence for impacts of synchrony with budburst on survival of larval Lepidoptera, previous studies of adult Geometridae and Noctuidae found no correlations between insect phenology and population variability.
2. We surveyed larval Lepidoptera feeding on Quercus alba and Q. velutina in Missouri from 1993 to 2003 and examined population variability, measured as the coefficient of variation of population density (CV), in a subset of abundant species. We compared CV values among species whose larvae feed only in spring, early summer, mid-summer, late summer, or all season. We predicted that univoltine species whose larvae eclose and complete development in spring during leaf expansion would have higher variability than species feeding later in the season, having multiple generations, or having longer development times.
3. As predicted and consistent with hypotheses, spring-feeding species had CV values 32% higher than species feeding in summer months. Coefficients of variation were also 34% higher in leaf-rolling and mining guilds compared with free-feeders, suggesting that mobile species may compensate for asynchrony with budburst by dispersing to higher quality plants or plant parts. Multivoltine species, however, did not differ from univoltine species in population variability.
4. Our results suggest that asynchrony with plant phenology and factors that might exacerbate it, such as climate change, will have the largest impacts on the dynamics of spring-feeding Lepidoptera, particularly species with limited mobility.     

Polymorphic microsatellite markers in the painted dragon lizard,Ctenophorus pictus

We isolated eight polymorphic microsatellite markers from the painted dragon, Ctenophorus pictus, from a genomic library simultaneously enriched for a suite of di‐, tri‐ and tetranucleotide repeat units. Genetic variation was assessed in 40 individuals from populations in Victoria and South Australia. The number of alleles per locus ranged from four to 45 with observed heterozygosity ranging from 0.23 to 0.95. These markers will be useful for studies of natural and sexual selection and the effects of habitat fragmentation in semiarid Australia.     

Evaluation of assisted colonization strategies under global change for a rare,fire‐dependent plant

As a clear consensus is emerging that habitat for many species will dramatically reduce or shift with climate change, attention is turning to adaptation strategies to address these impacts. Assisted colonization is one such strategy that has been predominantly discussed in terms of the costs of introducing potential competitors into new communities and the benefits of reducing extinction risk. However, the success or failure of assisted colonization will depend on a range of population‐level factors that have not yet been quantitatively evaluated – the quality of the recipient habitat, the number and life stages of translocated individuals, the establishment of translocated individuals in their new habitat and whether the recipient habitat is subject to ongoing threats all will play an important role in population persistence. In this article, we do not take one side or the other in the debate over whether assisted colonization is worthwhile. Rather, we focus on the likelihood that assisted colonization will promote population persistence in the face of climate‐induced distribution changes and altered fire regimes for a rare endemic species. We link a population model with species distribution models to investigate expected changes in populations with climate change, the impact of altered fire regimes on population persistence and how much assisted colonization is necessary to minimize risk of decline in populations of Tecate cypress, a rare endemic tree in the California Floristic Province, a biodiversity hotspot. We show that assisted colonization may be a risk‐minimizing adaptation strategy when there are large source populations that are declining dramatically due to habitat contractions, multiple nearby sites predicted to contain suitable habitat, minimal natural dispersal, high rates of establishment of translocated populations and the absence of nonclimatic threats such as altered disturbance regimes. However, when serious ongoing threats exist, assisted colonization is ineffective.     

Septal fracture in Nautilus: implications for cephalopod paleobathymetry

Analysis of septal geometry, as embodied in the septal strength index model developed by Westermann (1973, Lethaia 6). , has become a prime avenue for estimating living depths of fossil cephalopods. We have examined the fracturing of Nautilus septa, and its bearing on strength index, by inducing septal rupture under the action of hydrostatic pressure. We found that: (1) septa which actually fail under pressure are not generally weakest as defined by their strength indices; (2) septal strength as defined by the strength index is not correlated with rupture pressure; and (3) most instances of septal failure originate in septal sutures, not in the septa. These results indicate that: (1) septal strength index does not yield wholly reliable strength or depth estimates; and (2) the shortcomings of the strength index model stem from its inability to account for complexities of mechanical failure in morphologically complex cephalopod shells.     

Fishing and the Sexual Division of Labor among the Meriam

Do men and women forage differently because they are cooperatively responding to children's requirements for care or because they are differentially sensitive to variance? In this article, I examine how care trade-offs and variance contribute to gender differences in fishing strategies among Torres Strait Islanders (Meriam). Women's fishing had lower failure rates, coefficients of variation, and frequencies of sharing than men's fishing. Men and women responded to trade-offs between mean and variance differently: Women spent less time on high mean–high variance activities, men less time on high mean–low variance activities. Although child-care trade-offs affected time allocation to different fishing activities among women, they did not affect differences in time allocation between the sexes. These results support previous work implicating variance and sharing frequency as important resource currencies shaping gender differences in subsistence decisions, and they offer challenges to a general model of the division of labor predicated on economic notions of specialization as increasing production efficiency.