TGLE Vol. 51 nos. 3 & 4 full issue

TGLE Vol. 51 nos. 3 & 4 full issu

Effects of large herbivores on grassland arthropod diversity

Both arthropods and large grazing herbivores are important components and drivers of biodiversity in grassland ecosystems, but a synthesis of how arthropod diversity is affected by large herbivores has been largely missing. To fill this gap, we conducted a literature search, which yielded 141 studies on this topic of which 24 simultaneously investigated plant and arthropod diversity. Using the data from these 24 studies, we compared the responses of plant and arthropod diversity to an increase in grazing intensity. This quantitative assessment showed no overall significant effect of increasing grazing intensity on plant diversity, while arthropod diversity was generally negatively affected. To understand these negative effects, we explored the mechanisms by which large herbivores affect arthropod communities: direct effects, changes in vegetation structure, changes in plant community composition, changes in soil conditions, and cascading effects within the arthropod interaction web. We identify three main factors determining the effects of large herbivores on arthropod diversity: (i) unintentional predation and increased disturbance, (ii) decreases in total resource abundance for arthropods (biomass) and (iii) changes in plant diversity, vegetation structure and abiotic conditions. In general, heterogeneity in vegetation structure and abiotic conditions increases at intermediate grazing intensity, but declines at both low and high grazing intensity. We conclude that large herbivores can only increase arthropod diversity if they cause an increase in (a)biotic heterogeneity, and then only if this increase is large enough to compensate for the loss of total resource abundance and the increased mortality rate. This is expected to occur only at low herbivore densities or with spatio-temporal variation in herbivore densities. As we demonstrate that arthropod diversity is often more negatively affected by grazing than plant diversity, we strongly recommend considering the specific requirements of arthropods when applying grazing management and to include arthropods in monitoring schemes. Conservation strategies aiming at maximizing heterogeneity, including regulation of herbivore densities (through human interventions or top-down control), maintenance of different types of management in close proximity and rotational grazing regimes, are the most promising options to conserve arthropod diversity

Understanding drivers of species distribution change: a trait-based approach

The impacts of anthropogenic environmental change on biodiversity are well documented, with threats such as habitat loss and climate change identified as causes of change in species distributions. The high degree of variation in responses of species to environmental change can be partly explained through comparative analyses of species traits. I carried out a phylogenetically informed trait-based analysis of plant range change in Britain, discovering that traits associated with competitive ability and habitat specialism both explained variation in range changes. Competitive, habitat generalists out-perform ed species specialised to nutrient-poor conditions; a result which can be attributed to the impact of agricultural intensification in Britain. A limitation of the comparative approach is that the models do not directly test the impact of environmental change on species distribution patterns, but instead infer potential impacts. I tested the potential of comparative analyses from a spatial context by conducting a spatial analysis of plant distribution change in Britain, examining the direct impact of environmental change on the spatial distribution of the trait characteristics of species that have gone locally extinct. I discovered a loss of species associated with nitrogen poor soils in regions that had an increase in arable land cover, a result that supports the results from the trait-based analysis of plant range change and demonstrates that comparative studies can accurately infer drivers of distribution change. I found that the cross-region transferability of trait-based models of range change to be related to land cover similarity, highlighting that the trait-based approach is dependent on a regional context. Additionally, I discovered that traits derived from distribution data were significant predictors of range shift across many taxonomic groups, out-performing traditional life history traits. This thesis highlights the potential of the data accumulated through the increased public participation in biological recording to address previously unanswerable ecological research questions.Open Acces

The Native Plants of Ohio

PDF pages: 5

The Inheritance of Diagnostic Larval Traits for Interspecific Hybrids of \u3ci\u3ePapilio Canadensis\u3c/i\u3e and \u3ci\u3eP. Glaucus\u3c/i\u3e (Lepidoptera: Papilionidae)

Traits distinguishing the closely related tiger swallowtail butterfly species, Papilio canadensis and P. glaucus, include fixed differences in diagnostic sex-linked and autosomal allozymes as well as sex-linked diapause regulation, and sex-linked differences in oviposition behavior. Larval detoxification abilities for plants of the Salicaceae and Magnoliaceae families are dramatically different and basically diagnostic as well. The distinguishing morphological traits of the adults and larvae have not been genetically characterized. Here we describe the segregation of diagnostic larval banding traits in offspring from the 2 species in their hybrid and reciprocal backcross combinations. Elucidation of genetic basis, and linkage relationships of a suite of distinguishing biochemical, physiological, morphological, and ecological traits with regard to their geographic concordance across the hybrid zone is fundamental to understanding the pattern and process of speciation

Diapause Dynamics And Host Plant Utilization of \u3ci\u3eColias Philodice, Colias Interior\u3c/i\u3e and Their Hybrids (Lepidoptera: Pieridae)

Abnormal diapause dynamics and, to a lesser extent, reduced efficiency of host utilization by hybrid larvae constitute potential post-zygotic barriers to gene flow between a multivoltine legume-feeder, Colias philodice (Lepidoptera: Pieridae) and a univoltine Vaccinium-feeder, C. interior. At the time when C. interior larvae enter diapause, approximately 50% of hybrid larvae ceased feeding but did not enter diapause, and subsequently starved. Hybrid larvae readily accepted the host plants of both parental species. However, relative to C. philodice, hybrid larvae displayed a significantly reduced fifth instar relative growth rate (RGR) when fed the primary legume host, Medicago sativa. Reduced growth of hybrid larvae was attributable to both reduced relative consumption rate (RCR) and reduced efficiency of conversion of digested food (ECD), but not to reduced digestive efficiency (AD). Relative to C. interior, hybrid larvae fed Vaccinium myrtilloides displayed reduced pupal weight and reduced ECD. These results may explain in part why all known naturally­ occurring hybrids among North American Colias arise from parental species with similar host plant ranges and diapause strategies

Spatial Synchrony in Wisconsin Karner Blue (Lepidoptera: Lycaenidae) Populations

We analyzed geographic patterns of Karner blue (Lycaeides melissa samuelis Nabokov, Lepidoptera: Lycaenidae) population fluctuations in summer broods in central and northwestern Wisconsin and spring+summer broods in central Wisconsin. We removed possible effects of population trends by analyzing residuals from a regression of each site’s population index vs. year. We then calculated correlation coefficients (r) of these residuals for all site-pairs separately for 1992- 2005 (26 sites, N = 325 site-pairs), 1995-2005 (21 sites, N = 210), and 1998-2005 (14 sites, N = 91). We analyzed patterns in these r values relative to distance between sites using correlations vs. distance and using pairwise comparisons of different distance categories (0-3 km up to 223-264 km apart). Karner blues showed significant (P \u3c 0.05) population synchrony over all distances. Spatial autocorrelation was strongest among sites \u3c3 km apart, then gradually leveled off at greater distances. Statistical power increased when we added three years but the number of sites did not decrease greatly (1995-2005 vs. 1998-2005 analyses) and when using an annual index combining spring+summer indices instead of just summer. The spatial autocorrelation extending over the entire study region suggests that environmental factors like weather provide some synchronization of Karner blue populations. Their much higher local synchrony is consistent with the species’ short dispersal distance. Their local and regional spatial autocorrelation increases the likelihood of correlated local extinctions during low fluctuation broods, especially when these coincide with unfavorable weather or adverse habitat events

Revisiting the Andean butterfly Eryphanis zolvizora group (Lepidoptera, Nymphalidae) : one or several species?

Eryphanis zolvizora (Hewitson, 1877) is a rare Andean endemic butterfly, described from Bolivia, which has been historically classified either as a unique species, or as part of a group of three allopatric species from Bolivia, Ecuador and Colombia. In this paper, the group is revised using more than 200 specimens housed in 35 European and North and South American public and private collections. For the first time, the presence of the group in Western Ecuador and Venezuela is confirmed, and important data on Peruvian populations are provided. In some populations, individual variations of genitalia are observed. Nevertheless, male genitalia allow the distinction of four geographical groups. Considering also habitus characters, eight taxa are distinguished and considered to be subspecies, of which five are new: Eryphanis zolvizora inca ssp. nov., Eryphanis zolvizora chachapoya ssp. nov., Eryphanis zolvizora casagrande ssp. nov., Eryphanis zolvizora reyi ssp. nov., and Eryphanis zolvizora isabelae ssp. nov. In the present state of knowledge, these taxa are allopatric, except for a possible geographic overlap in central Peru, where data are insufficient to prove sympatry. The “several subspecies vs. several species” dilemma is discussed, considering its impact for conservation action and policies