Landscape discontinuities influence gene flow and genetic structure in a large, vagile Australian mammal, Macropus fuliginosus

Large vagile mammals typically exhibit little genetic structuring across their range, particularly when their habitat is essentially continuous. We investigated the population genetic structure of a large vagile Australian macropodid, Macropus fuliginosus, which is continuously distributed across most of southern Australia, using nine highly polymorphic nuclear microsatellite loci. Five distinct genetic units were identified across the range, four on the mainland and one on Kangaroo Island. In addition to the predicted historic Nullarbor Plain Barrier, two unexpected mainland barriers to gene flow were identified. Both were associated with landscape discontinuities (Swan River, Flinders Ranges), which appear within the dispersal capabilities of M. fuliginosus. Typical of large vagile mammals, M. fuliginosus displays high genetic diversity (with the exception of an insular population) and weak genetic structuring (within genetic units). However, the expansion of M. fuliginosus from southwestern Australia during the Pleistocene has resulted in significantly reduced genetic diversity in eastern populations. No significant sex-biased dispersal was detected, although differences in habitat, densities and climatic conditions between the eastern and western regions of the range appear to influence dispersal with the effects of isolation by distance only evident in the west. These results suggest that the biogeography of southern Australia is more complex than previously thought and reveal that seemingly minor landscape features can significantly impact genetic structuring in large vagile mammals.     

Fire frequency and biodiversity conservation in Australian tropical savannas: implications from the Kapalga fire experiment

Abstract Every year large proportions of northern Australia's tropical savanna landscapes are burnt, resulting in high fire frequencies and short intervals between fires. The dominant fire management paradigm in these regions is the use of low‐intensity prescribed fire early in the dry season, to reduce the incidence of higher‐intensity, more extensive wildfire later in the year. This use of frequent prescribed fire to mitigate against high‐intensity wildfire has parallels with fire management in temperate forests of southern Australia. However, unlike in southern Australia, the ecological implications of high fire frequency have received little attention in the north. CSIRO and collaborators recently completed a landscape‐scale fire experiment at Kapalga in Kakadu National Park, Northern Territory, Australia, and here we provide a synthesis of the effects of experimental fire regimes on biodiversity, with particular consideration of fire frequency and, more specifically, time‐since‐fire. Two recurring themes emerged from Kapalga. First, much of the savanna biota is remarkably resilient to fire, even of high intensity. Over the 5‐year experimental period, the abundance of most invertebrate groups remained unaffected by fire treatment, as did the abundance of most vertebrate species, and we were unable to detect any effect of fire on floristic composition of the grass‐layer. Riparian vegetation and associated stream biota, as well as small mammals, were notable exceptions to this general resilience. Second, the occurrence of fire, independent of its intensity, was often the major factor influencing fire‐sensitive species. This was especially the case for extinction‐prone small mammals, which have suffered serious population declines across northern Australia in recent decades. Results from Kapalga indicate that key components of the savanna biota of northern Australia favour habitat that has remained unburnt for at least several years. This raises a serious conservation concern, given that very little relatively long unburnt habitat currently occurs in conservation reserves, with most sites being burnt at least once every 2 years. We propose a conservation objective of increasing the area that remains relatively long unburnt. This could be achieved either by reducing the proportion of the landscape burnt each year, or by setting prescribed fires more strategically. The provision of appropriately long unburnt habitat is a conservation challenge for Australia's tropical savanna landscapes, just as it is for its temperate forests.     

Testing for selection on the androgen-binding protein in the Danish mouse hybrid zone

The three peripheral subspecies of the house mouse Mus musculus have fixed specific variants of the androgen-binding protein (ABP) that have been proposed to be part of a recognition mechanism that could participate in sexual isolation between the subspecies. We tested for selection on Abpa by characterizing the pattern of Abpa introgression across a transect of the hybrid zone between M. m. musculus and M. m. domesticus in Jutland. On the musculus side, the cline for Abpa resembled that of a nearly neutral allozyme more than that of strongly selected X and Y chromosome markers. However, the high central step which displaces the tail of introgression of Abpa to higher frequencies was best accounted for by linkage to a locus under strong selection against hybrids. Still, we cannot exclude that this pattern results from weak selection against Abpa in the tail of introgression, which would be compatible with an assortative choice mechanism. On the domesticus side there was little introgression close to the hybrid zone, presumably due to a geographical barrier to migration. However, substantial frequencies of musculus alleles occurred further away, suggesting mixed colonization patterns as well as flow across the hybrid zone.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 84 , 447–459.     

Light absorption by phytoplankton and chromophoric dissolved organic matter in the drainage basin and estuary of the Neuse River, North Carolina (U.S.A.)

1. We examined the absorption of solar radiation by phytoplankton and chromophoric dissolved organic matter (CDOM) taking into account riparian shading in the rivers, reservoirs, swamps of the Neuse River Estuary and its drainage basin. 2. In the streams, CDOM typically absorbed 55 and 64% of photons in the spectral range of 400–700 nm (photosynthetically active radiation, PAR) and 500–600 nm, respectively. The large proportion of photons absorbed by CDOM indicates high potential for abiotic photochemial reactions in the 500–600 nm region. 3. Despite the high concentration of nutrients, phytoplankton contributed little (2%) to the total absorption of PAR in the streams. Small (<30 m wide) streams typically received only 7% of incident PAR that impinged onto the more exposed reservoirs and estuary. Riparian shading and the low contribution of phytoplankton to the total absorption resulted in conditions where phytoplankton absorbed nearly two orders of magnitude less PAR in the streams than in the estuary and reservoirs. 4. The results indicated that riparian shading and non‐algal absorbing components can significantly restrict phytoplankton production in nutrient‐rich streams with a high concentration of CDOM flowing throughout forested catchments.     

Interrelationships and diversification of Argynnis Fabricius and Speyeria Scudder butterflies

Diverse radiations of insects are often associated with adaptations to host plants, and well‐resolved phylogenetic relationships are required to fully understand them. Palearctic Argynnis and related subgenera, together with North American Speyeria butterflies make up a radiation whose species hypotheses are confounded by shared wing colour patterns between sympatric populations of closely related recognized species. Previous studies of this group indicate that Speyeria is a lineage within Argynnis, but sampling in these studies has either involved too few Speyeria species or incomplete sampling of Argynnis species. Thus, no comprehensive phylogenetic analysis exists for all members that answers the question of monophyly of Speyeria, or other subgeneric taxa, and their relationship to Argynnis species. We completed a phylogenetic analysis of all North American Speyeria species and all but one species within Argynnis, using one mitochondrial (cytochrome c oxidase I, COI) and four nuclear genes [elongation factor 1 alpha (EF1α), wingless (WG), glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH), and ribosomal protein S5 (RPS5)]. The results indicate three major lineages within Argynnis s.l.: two Palearctic and one containing both Palearctic and Nearctic species. In summary, the phylogenetic analyses suggest the need for reorganization into three natural groups: Argynnis, Fabriciana and Speyeria. Within each of these genera the phylogenetic hypothesis indicates an evolutionary history marked by rapid diversification and potential extinction, followed by ongoing lineage sorting. The position of North American Speyeria is nested within the Palearctic lineages, which indicates that the radiation began in Asia and was fuelled by existing Viola diversity in North America. Dating analyses of Viola and Speyeria corroborate this hypothesis. The current North American Speyeria species are mixed on the tree, indicating a recent and ongoing radiation. These results provide needed clarity on the evolution of this group, which contains species of conservation concern.     

中国裂隙衣属地衣（文字衣科）的初步研究

在中国文衣科地衣系统研究中,对裂隙衣属Fissurina地衣进行了订正,报道了16种,其中中国新记录种3个,即连绵裂隙衣F. consentanea、球孢裂隙衣F. globulifica和皱体裂隙衣F. insidiosa。建议4个异名,即Fissurina isidiata Z.F. Jia 为Platythecium dimorphodes (Nyl.) Staiger的异名;Fissurina marginata Staiger为Fissurina elaocarpa (A.W. Archer) A.W. Archer的异名;Graphis canlaonensis Vain.为Fissurina consentanea Nyl.的异名;Graphis glauca Müll. Arg.为Fissurina dumastii Müll. Arg.的异名。本文提供了中国裂隙衣属每个种的描述和分布,并提供了鉴定检索表。     

Comparative anatomy and morphology of fertile complexes of Prumnopitys and Afrocarpus species (Podocarpaceae) as revealed by histology and NMR imaging, and their relevance to systematics

Fertile complexes (individual reproductive units of ovulate cones) of three Prumnopitys species and Afrocarpus falcatus (Podocarpaceae) were subjected to histological examination and non-destructive NMR imaging. The latter technique allowed the display, frame-by-frame analysis and electronic 'dissection' of internal structures such as the number and courses of vascular traces and resin canals and their morphology. Characters of these internal structures distinguished all three Prumnopitys species from each other and thus were shown to be taxonomically diagnostic. Fertile complexes of Prumnopitys andina and P. taxifolia were most similar, possessing simple vascular traces and few unbranched resin canals. Those of P. ferruginea were very different and possessed an interconnected network of resin ducts within the sarcotesta. These findings are congruent with relationships inferred from molecular phylogenetic studies, in which two subclades were recovered within Prumnopitys . The anatomy of the female fertile complexes of Afrocarpus falcatus was very distinct from all Prumnopitys species analysed. Its most distinctive feature was the existence of a complex network of radial vascular strands originating from within the outer layers of the sarcotesta and penetrating the inner layers of the fertile complex. The surface texture and morphology of the sclerotesta of the seed was also unique to each species.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 145 , 295–316.