Criticisms Biologically Unwarranted and Analytically Irrelevant: Reply to Rominger et al.

ABSTRACT The criticisms of Rominger et al. (2008) of our retrospective analysis of desert bighorn sheep (DBS; Ovis canadensis mexicana) dynamics in the San Andres Mountains of south-central New Mexico, USA, contained many biological errors and analytical oversights. Herein, we show that Rominger et al. (2008) 1) overstated both magnitude and potential effect of predator removal; 2) incorrectly claimed that our total precipitation (TP) model did not fit the data when TP correctly classed ≥66% of subsequent population increases and declines (P ≥0.063); 3) presented a necessary prerequisite of the exponential model (serial correlation between N_t and N_t+1) as the key relationship in the DBS data, when it merely reflected that DBS are strongly K-selected and was irrelevant to our hypothesis tests specific to factors affecting the instantaneous rate of population increase (r); 4) greatly oversimplified relationships among precipitation, arid environments, and DBS; and 5) advocated a time for collection of lamb/female (L/F) ratio data that was unrelated to any meaningful period in the biological year of DBS and consequently presented L/F ratio data unrelated to observed dynamics of DBS. In contrast, the L/F ratios used in Bender and Weisenberger (2005) correctly predicted annual changes and were correlated with long-term population rates of change.     

Nutritional niche separation in coexisting bog species demonstrated by 15N‐enriched simulated rainfall

Empodisma minus and Sporadanthus ferrugineus (both Restionaceae) coexist in New Zealand raised bogs, yet Sporadanthus have significantly more depleted ¹⁵N natural abundance signatures than coexisting Empodisma. Their root systems are spatially separated with Empodisma having a thick surface layer of about 50 mm of cluster roots overlying the deeper Sporadanthus roots. We hypothesized this root displacement allows Empodisma to preferentially access the primary N input from rainfall, thus establishing niche separation, and tested this using tracer stable isotopes. We aerially applied 1.6 mmol m^?2 of ¹⁵N as (NH₄)₂SO₄ chased by deionized water to simulate a rainfall event of 34 L m^?2. Root/peat matrix cores were harvested after 5 h and analysed for ¹⁵N uptake. Approximately 80% of the tracer applied was recovered in the cores, with 90% of this recovered in the upper Empodisma cluster root layer. Seven weeks after application, young shoots of Empodisma were significantly enriched (mean δ¹⁵N = +7.21‰; reference = ?0.42‰), whereas those of coexisting Sporadanthus were not (mean δ¹⁵N = ?2.76‰; reference = ?4.24‰). However, we were unable to quantify the ¹⁵N uptake because of the dilution effect of the large biomass. We calculated the contribution of biological nitrogen fixation as a possible alternative source of N in achieving niche separation. The acetylene reduction assay showed minor amounts of nitrogenase activity are associated with Empodisma and Sporadanthus roots (equivalent to 0.045 ± 0.019 and 0.104 ± 0.017 kg N ha^?1 year^?1 respectively). Our results suggest that the species acquire nutrients from different rooting zones, with Empodisma accessing nutrients at the surface from rainfall and Sporadanthus accessing nutrients from mineralization in deeper peat layers. Such niche differentiation probably facilitates species coexistence and may provide a mechanism for slowing the rate of competitive displacement during long‐term succession.     

PERM: a computer program to detect structuring factors in social units

perm is a permutation program designed to detect statistical connections between grouping structures and grouping factors or correlates. Groups may be of various kinds such as herds, flocks, schools and mating couples provided they make up meaningful social units. Relatedness, population membership and genotypic contents are among several aggregating variables which may be processed. Typically, perm takes in a collection of grouped data and outputs a P value. The latter is computed on the basis of random membership among groups (H_O). All files, including input, output and program, are of Excel type (.xls). perm can be downloaded free of charge at: http://www.bio.ulaval.ca/louisbernatchez/downloads.htm .     

Does competition with wind‐pollinated species alter Echium plantagineum's attractiveness to a common pollinator Bombus terrestris?

1. In insect‐pollinated plants, pollinator attraction is influenced by flowers (e.g. number, size) and their associated rewards (e.g. pollen, nectar). These traits can depend on plant interactions. Indeed, below‐ground competition between plants can lead to a decrease in flower or reward production in insect‐pollinated species. 2. Wind‐pollinated plants, in particular, which are almost never studied in plant–pollinator networks, can alter insect‐pollinated plants' attractiveness through competition for nutrients. The response of pollinators to such changes has never been investigated. 3. A pot experiment was carried out in which an insect‐pollinated species, Echium plantagineum, was grown in binary mixture with three wind‐pollinated species selected to exert a panel of competitive interactions. Below‐ground competition was controlled using dividers limiting interspecific root competition. Floral traits of E. plantagineum (i.e. flower production, floral display size, flower size and nectar production) were measured. For each species mixture, the visits (i.e. first visit, number of visits, 10‐min sequences) of Bombus terrestris individuals released in a flight cage containing two pots were followed, one with and one without below‐ground competition. 4. Below‐ground competition significantly affected nectar's sucrose concentration but did not influence flower and nectar production. Likewise, pollinator visits were not influenced by below‐ground competition. Competitor identity significantly influenced flower and reward production of E. plantagineum, with a decrease in the presence of the most competitive wind‐pollinated species. A tendency for faster flower visitation events was also detected in the presence of the least competitive competitor. This study raises new questions regarding the influence of wind‐pollinated plants on plant–pollinator interactions.     

Juvenile cranial anatomy of Nimravidae (Mammalia, Carnivora): biological and phylogenetic implications

The anatomy of the spectacular sabretoothed carnivorans has been studied many times. Their behavioural and biomechanical implications are well known in adults, but not in juvenile individuals, which are poorly represented in the fossil record. This work reports on a newly discovered Hoplophoneini (Nimravidae Nimravinae) of 5–6 months of age, which represents the earliest and one of the most complete juvenile crania discovered. We discuss and compare the juvenile anatomy of Palaeogene nimravids relative to that of other mammals, especially other carnivorans including the Miocene nimravids (i.e. Barbourofelinae). We also discuss the ontogenetic development of this individual and other sabretoothed predators, which provides important data for reconstructing the biology of these extinct predators. Our study of the juvenile anatomy of the Hoplophoneini reveals an original association of basicranial features: the ectotympanic rotates away from the cranium earlier than in other mammals, which may be an additional autapomorphy distinguishing the Palaeogene Nimravidae from other Carnivora; within Palaeogene Nimravidae, at a similar ontogenetic stage, there is a major difference in development and maximum ventral extension of ossification of the caudal entotympanic; in contrast to the Miocene nimravid Barbourofelis, there is no strong relationship between the eruption of the upper canines and the development of other sabretoothed features (especially the mandibular flange) in the individual described. These results confirm the conclusions of recent studies which suggested that Palaeogene Nimravidae (Nimravinae) and Miocene Nimravidae (Barbourofelinae) are not closely related. Muscular reconstruction and biomechanical models also confirmed that juvenile individuals were probably not able to kill or hunt any prey. They may have fed on carcasses, eating muscles by using the incisors, and associated with a pulling or twisting action of neck. © 2003 The Linnean Society of London. Zoological Journal of the Linnean Society, 2003, 138 , 477–493.     

New Paleonura and Pronura species (Collembola, Neanurinae) from Thailand

Five new species of Neanurinac collemboles arc described from Doi Inthanon Mountain (Thailand): Paleonura dilatata sp.n., Paleonura lanna sp.n., Paleonura monochaeta sp.n., Pronura dorsolateralis sp.n. and Pronura ornata sp.n.     

Carbon emissions from fires in tropical and subtropical ecosystems

Global carbon emissions from fires are difficult to quantify and have the potential to influence interannual variability and long‐term trends in atmospheric CO₂ concentrations. We used 4 years of Tropical Rainfall Measuring Mission (TRMM) Visible and Infrared Scanner (VIRS) satellite data and a biogeochemical model to assess spatial and temporal variability of carbon emissions from tropical fires. The TRMM satellite data extended between 38°N and 38°S and covered the period from 1998 to 2001. A relationship between TRMM fire counts and burned area was derived using estimates of burned area from other satellite fire products in Africa and Australia and reported burned areas from the United States. We modified the Carnegie‐Ames‐Stanford‐Approach (CASA) biogeochemical model to account for both direct combustion losses and the decomposition from fire‐induced mortality, using both TRMM and Sea‐viewing Wide Field of view Sensor (SeaWiFS) satellite data as model drivers. Over the 1998–2001 period, we estimated that the sum of carbon emissions from tropical fires and fuel wood use was 2.6 Pg C yr^?1. An additional flux of 1.2 Pg C yr^?1 was released indirectly, as a result of decomposition of vegetation killed by fire but not combusted. The sum of direct and indirect carbon losses from fires represented 9% of tropical and subtropical net primary production (NPP). We found that including fire processes in the tropics substantially alters the seasonal cycle of net biome production by shifting carbon losses to months with low soil moisture and low rates of soil microbial respiration. Consequently, accounting for fires increases growing season net flux by ～12% between 38°N and 38°S, with the greatest effect occurring in highly productive savanna regions.     

Tug of war between continental gene flow and rearing site philopatry in a migratory bird: the sex-biased dispersal paradigm reconsidered

Nonrandom dispersal has been recently advanced as a mechanism promoting fine-scale genetic differentiation in resident populations, yet how this applies to species with high rates of dispersal is still unclear. Using a migratory species considered a classical example of male-biased dispersal (the greater snow goose, Chen caerulescens atlantica ), we documented a temporally stable fine-scale genetic clustering between spatially distinct rearing sites (5–30 km apart), where family aggregates shortly after hatching. Such genetic differentiation can only arise if, in both sexes, dispersal is restricted and nonrandom, a surprising result considering that pairing occurs among mixed flocks of birds more than 3000 km away from the breeding grounds. Fine-scale genetic structure may thus occur even in migratory species with high gene flow. We further show that looking for genetic structure based on nesting sites only may be misleading. Genetically distinct individuals that segregated into different rearing sites were in fact spatially mixed during nesting. These findings provide new, scale-dependent links between genetic structure, pairing, and dispersal and show the importance of sampling different stages of the breeding cycle in order to detect a spatial genetic structure.     

Spatio-temporal population genetic structure of the parasitic mite Spinturnix bechsteini is shaped by its own demography and the social system of its bat host

Information about the population genetic structures of parasites is important for an understanding of parasite transmission pathways and ultimately the co-evolution with their hosts. If parasites cannot disperse independently of their hosts, a parasite's population structure will depend upon the host's spatial distribution. Geographical barriers affecting host dispersal can therefore lead to structured parasite populations. However, how the host's social system affects the genetic structure of parasite populations is largely unknown. We used mitochondrial DNA (mtDNA) to describe the spatio-temporal population structure of a contact-transmitted parasitic wing mite ( Spinturnix bechsteini ) and compared it to that of its social host, the Bechstein's bat ( Myotis bechsteinii ). We observed no genetic differentiation between mites living on different bats within a colony. This suggests that mites can move freely among bats of the same colony. As expected in case of restricted inter-colony dispersal, we observed a strong genetic differentiation of mites among demographically isolated bat colonies. In contrast, we found a strong genetic turnover between years when we investigated the temporal variation of mite haplotypes within colonies. This can be explained with mite dispersal occuring between colonies and bottlenecks of mite populations within colonies. The observed absence of isolation by distance could be the result from genetic drift and/or from mites dispersing even between remote bat colonies, whose members may meet at mating sites in autumn or in hibernacula in winter. Our data show that the population structure of this parasitic wing mite is influenced by its own demography and the peculiar social system of its bat host.