Population structure in the catfish Trichogenes longipinnis: drift offset by asymmetrical migration in a tiny geographic range

Based on population genetic theory and empirical studies of small populations, we expect that species with very small ranges (narrow endemics) will exhibit reduced genetic diversity, increasing their susceptibility to the negative effects of genetic homogeneity. Although this pattern of reduced diversity applies to most narrow endemics, conservation biologists have yet to identify a general pattern for the degree of spatial population genetic structure expected in species with very small ranges. In part, this is because the degree of population structure within narrow endemics will be highly variable depending on the equilibrium between the homogenizing effects of dispersal and the diversifying effects of drift and local selection in small populations, thus precluding general predictions about the relative importance of small range, small population sizes, and habitat patchiness for maintaining genetic diversity in narrowly-distributed species. We document a striking example of high population structure in the tiny geographic range of a stream-dwelling catfish, Trichogenes longipinnis , endemic to the Atlantic Forest of Brazil. The maintenance of this diversity results from a combination of asymmetrical and limited dispersal, and drift in small populations. Our results highlight the need to understand population structure, and not only overall genetic diversity, of narrowly-distributed species for their conservation planning.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 259–274.     

A Laurentian Iocrinus Hall (Crinoidea,Disparida) in the Dapingian or Darriwilian (Middle Ordovician,Arenig) of Oman

Abstract: Early and early Middle Ordovician crinoids are rare globally, and are best known from North America and the British Isles. The first Arenig crinoid from the Arabian Peninsula is Iocrinus sp. cf. I. subcrassus (Meek and Worthen), known from two near‐complete individuals, and numerous fragmentary specimens and ossicles. These are the stratigraphically oldest Iocrinus specimens, and provide an unexpected extension of the palaeogeographical range of a genus known otherwise from slightly younger deposits in Laurentia (North America) and Avalonia (Wales). The Oman specimens differ from Gondwanan Heviacrinus melendezi Gil Cid et al., currently classified as a maennilicrinid, but morphologically close to Iocrinus, in having arms that branch at least seven times instead of four and in having columnals typical of Iocrinus. Three species from Wales and the Welsh Borders, previously placed in Iocrinus, but differing in having smooth, conical dorsal cups, are reclassified as Margoiocrinus Donovan gen. nov., type species Iocrinus shelvensis Ramsbottom.     

Seasonal hysteresis of net ecosystem exchange in response to temperature change: patterns and causes

Understanding how net ecosystem exchange (NEE) changes with temperature is central to the debate on climate change‐carbon cycle feedbacks, but still remains unclear. Here, we used eddy covariance measurements of NEE from 20 FLUXNET sites (203 site‐years of data) in mid‐ and high‐latitude forests to investigate the temperature response of NEE. Years were divided into two half thermal years (increasing temperature in spring and decreasing temperature in autumn) using the maximum daily mean temperature. We observed a parabolic‐like pattern of NEE in response to temperature change in both the spring and autumn half thermal years. However, at similar temperatures, NEE was considerably depressed during the decreasing temperature season as compared with the increasing temperature season, inducing a counter‐clockwise hysteresis pattern in the NEE–temperature relation at most sites. The magnitude of this hysteresis was attributable mostly (68%) to gross primary production (GPP) differences but little (8%) to ecosystem respiration (ER) differences between the two half thermal years. The main environmental factors contributing to the hysteresis responses of NEE and GPP were daily accumulated radiation. Soil water content (SWC) also contributed to the hysteresis response of GPP but only at some sites. Shorter day length, lower light intensity, lower SWC and reduced photosynthetic capacity may all have contributed to the depressed GPP and net carbon uptake during the decreasing temperature seasons. The resultant hysteresis loop is an important indicator of the existence of limiting factors. As such, the role of radiation, LAI and SWC should be considered when modeling the dynamics of carbon cycling in response to temperature change.     

Phylogenetic analysis of Micrathena and Chaetacis spiders (Araneae: Araneidae) reveals multiple origins of extreme sexual size dimorphism and long abdominal spines

The phylogenetic relationships amongst the New World spiny orb‐weaving spiders Micrathena and Chaetacis were assessed through parsimony and Bayesian analyses of morphological characters. A total of 146 characters was scored for ten outgroup taxa and 37 Micrathena and four Chaetacis species. The results indicate that Chaetacis nests within Micrathena and we propose Chaetacis as a junior synonym of Micrathena. Twelve subgeneric species groups of Micrathena are recognized and diagnosed. Species with extremely long spines evolved at least eight times in the genus and we suggest that this may be related to antipredator defences. Micrathena is primitively sexually monomorphic and extreme sexual size dimorphism has arisen at least six times in the genus. Most of these events are because of enlargement of the female in relation to the ancestral size, although in two cases sexual dimorphism was attained through male reduction, adding more data to the ‘giant females’ vs. ‘dwarf males’ controversy. The genus is probably of South American origin and has repeatedly invaded Central and North America. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 166 , 14–53.     

Differential pollination success in the course of individual flower development and flowering time in Gentiana pneumonanthe L. (Gentianaceae)

The effect of flowering time and anthesis stage on fecundity of Gentiana pneumonanthe L. (Gentianaceae) in a greenhouse experiment was studied. The species is self-compatible, not apomictic, and rarely self-pollinates spontaneously. On average, flowers lived for 11.4 days, starting with a male stage of 3.6 and continuing with a female stage of 7.9 days. Pollen viability was highest during the first two days of the male stage, but never exceeded 50%. Seed-set from cross-pollination was higher earlier in the flowering period (77%) than later (63Vo). For self-pollinations, no significant difference was observed. The success of hand-pollinations declined dramatically after the fourth day of the female stage. Self-pollination yielded lower seed-set on the first day of the female stage than on the following three days. Also, there was a significant difference in seed-set between self- and cross-pollinations (25% vs 55%, respectively) only on the first day. This suggests that selection against self pollen was stronger during the first stage of the female phase and weakened as the stylar tissue aged. In conclusion, two different ways to enhance outcrossing were observed: (1) within the population's flowering period, and (2) within an individual flower's lifespan. Both may have important effects on the genetic variability of G. pneumonanthe offspring under unfavourable conditions. Wese include small population size (associated with reduced pollinator service), general pollinator scarcity, or rainy summers.     

Systematic implications of wood and bark anatomy in the Pacific Island genus Meryta (Araliaceae)

Wood anatomy was examined in 16 species of Meryta (a genus of c . 35 species) and bark anatomy was studied in 12 species. All but two of these taxa form an assemblage corresponding to the Northern Arc clade, one of two major groups identified by a recent molecular phylogenetic study. M. sinclairii and M. tenuifolia (corresponding to the New Zealand/Fiji clade) differ distinctly by having more numerous simple perforation plates, multiseriate rays with few marginal rows, and the absence of sclerified cells in collapsed secondary phloem, a bark feature that has not yet been found elsewhere in Araliaceae. The increase in abundance of simple perforation plates in the wood of these two species is not accompanied by a decrease in the number of bars on scalariform perforation plates. The wood structure of Meryta bears a strong resemblance to members of the Pacific Schefflera clade, sharing similar ranges of variation of several features. Bark characters, such as the diameter of the cortical secretory canals, the types of crystal in cortical cells, the types of axial parenchyma cell in collapsed secondary phloem, and the presence of sheath cells by phloem rays, appear to be of diagnostic value for some species of Meryta .  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 153 , 363–379.     

Belowground infections of the invasive Phytophthora plurivora pathogen enhance the suitability of red oak leaves to the generalist herbivore Lymantria dispar

1. Globally, vast areas of forest are currently threatened by Lymantria dispar L. and Phytophthora species, which cause widespread declines and cascading ecological impacts. One important aim of evolutionary and ecological studies is to understand their interactions. 2. The present study tests whether Quercus rubra L. trees naturally infected with P. plurivora T. Jung & T.I. Burgess or free of infection are more suitable for L. dispar herbivory, and if relationships between L. dispar performance and herbivory may vary depending on whether trees are infected or free of infection. 3. In choice tests, the consumed area of leaves from trees infected by P. plurivora was four times larger than that from non‐infected trees, probably because the increased values of N, soluble protein, and water content observed in the leaves of infected trees enhanced acceptability. Although larval performance was better in Phytophthora‐infected trees, relationships between larval performance and defoliation did not significantly interact with the health status of trees. 4. The present results suggest that the impact of P. plurivora on natural and managed ecosystems may generate a positive feedback loop for oak decline. The link between the behavioural and physiological responses of L. dispar to infected trees and the population growth in nature deserves further investigation.     

Hair-Trap Efficacy for Detecting Mammalian Carnivores in the Tropics

Abstract: Direct studies of mammalian carnivores are challenging due to the animals' secretive nature and the high costs associated with their capture and handling. Use of noninvasive hair sampling to survey these reclusive species has great potential as an alternative, with wide applicability in ecology and conservation. Hair-trapping has been extensively used for focal studies of temperate mammals, but its use and applicability as a means to survey mammals in tropical environs has never been addressed. We evaluated the effectiveness of 2 hair-trap types and 2 scents along an elevational gradient within El Cielo Biosphere Reserve (ECBR, Mexico) to detect presence of carnivores. Hair-traps that used roofing nails as a hair-collecting surface collected more hairs and detected a greater number of species than did hair-traps that used velcro strips. Different scent treatments (commercial fragrance and catnip oil) did not differ for these same variables. Of successful nail hair-traps, 60% collected ≥20 hairs (max. = 439), providing enough material for DNA analyses. Hair-trap surveys detected 74% of the potential target mammal species at ECBR with only 19 days of field effort. Developing countries have limited budgets for biodiversity monitoring and hair-traps compare favorably with other methods with a high cost-benefit ratio. Hair-traps are inexpensive, portable, can be made with over-the-counter materials, and can be successfully used to collect data applicable to population and genetic studies of tropical carnivores.