Modelling the abundance of three key plant species in New Zealand hill-pasture using a decision tree approach

Decision tree models were developed to investigate and predict the relative abundance of three key pasture plants [ryegrass (Lolium perenne), browntop (Agrostis capillaris), and white clover (Trifolium repens)] with integration of a geographical information system (GIS) in a naturalised hill-pasture in the North Island, New Zealand, and were compared with regression models with respect to model fit and predictive accuracy. The results indicated that the decision tree models had a better model fit in terms of average squared error (ASE) and a higher percentage of adequately predicted cases in model validation than the corresponding regression models. These decision tree models clearly revealed the relative importance of environmental and management variables in influencing the abundance of these three species. Hill slope was the most significant environmental factor influencing the abundance of ryegrass while soil Olsen P and annual P fertilizer input were the most significant factors influencing the abundance of browntop, and white clover, respectively. Soil Olsen P of approximately 10 μg/g, or a slope of about 10.5° was critical points where the competition between ryegrass and browntop tended to come to an equilibrium. Integrating the decision tree models with a GIS in this study not only facilitated the model development and analyses, but also provided a useful decision support tool in pasture management such as in assisting precision fertilizer placement. The insights obtained from the decision tree models also have important implications for pasture management, for example, it is important to maintain a soil Olsen P higher than 10 μg/g in order to keep the dominance of ryegrass in the hill-pasture.     

Female mate choice determines reproductive isolation between sympatric butterflies

Animal courtship rituals are important for species recognition, and a variety of cues might be utilized to recognize conspecific mates. In this paper, we investigate different species-recognition mechanisms between two sympatric butterfly sister species: the wood white (Leptidea sinapis) and Real’s wood white (Leptidea reali). We show that males of both species frequently court heterospecific females both under laboratory and field conditions. The long-lasting elaborate courtships impose energetic costs, since the second courtship of males that were introduced to two subsequent conspecific females lasted on average only one fourth as long as the first courtship. In this paper, we demonstrate that premating reproductive isolation is dependent on female unwillingness to accept heterospecific mates. We studied female and male courtship behavior, chemical signaling, and the morphology of the sexually dimorphic antennae, one of the few male traits visible for females during courtship. We found no differences in ultraviolet (UV) reflectance and only small differences in longer wavelengths and brightness, significant between-species differences, but strongly overlapping distributions of male L. sinapis and L. reali antennal morphology and chemical signals and minor differences in courtship behavior. The lack of clear-cut between-species differences further explains the lack of male species recognition, and the overall similarity might have caused the long-lasting elaborate courtships, if females need prolonged male courtships to distinguish between con- and heterospecific suitors.     

Contest behaviour in the speckled wood butterfly (Pararge aegeria): seasonal phenotypic plasticity and the functional significance of flight performance

Although contemporary animal contest theory emphasises the importance of physical asymmetries in resolving disputes, such asymmetries do not obviously settle fights in all groups. Territorial male butterflies, for example, compete via elaborate non-contact aerial interactions in which success is determined by relative persistence. Prior research suggests that the resolution of these contests is not clearly related to physical variables such as body size or energy reserves. However, given that the contests involve elaborate aerial manoeuvres, one long-standing suggestion is that asymmetries in flight performance, and thus flight morphology, may be important. We addressed this hypothesis via a manipulative investigation into the biophysical correlates of contest success in the speckled wood butterfly, Pararge aegeria. This species possesses the ability for significant adaptive phenotypic plasticity in relevant flight morphological parameters. We took advantage of this plasticity to rear 90 individuals of markedly varying flight morphologies, which we then pitted against each other in a semi-controlled experimental fashion. Multiple logistic and lognormal analyses provided little evidence for the relevance of morphological parameters, including relative flight musculature, wing loading and wing aspect ratio (wing length relative to area), to the outcome and/or duration of experimental contests. Instead, we found a positive effect of age upon contest success. Given that ability for high acceleration is strongly linked to variation in these morphological parameters, our findings suggest that flight performance is not a strong determinant of resource-holding potential in this notably territorial butterfly.     

Recent Recovery of Lake Water Quality in Southern Québec Following Reductions in Sulfur Emissions

Since 1985, monitoring activities have been conducted in a networkof 43 lakes comprising the Québec portion of the Long-Range Transport of Airborne Pollutants (LRTAP) program. The results to date indicate that Québec lakes generally are responding positively to the generalized decline in precipitation sulfate (SO₄ ^2-), with 40 of the 43 lakes now showing steep declines in SO₄ ^2- concentrations. The drop in SO₄ ^2- was associated with a significant decrease in Ca²⁺ concentrations in 77% of the lakes (67% for Mg²⁺ concentrations). Overall, the acid-neutralizing capacity was increasing in 19 lakes and decreasing only in three, while 21 lakes showed no temporal trends. Compared with previous trend studies of the LRTAP-Québec network for the period of 1985–1993, the longer period (1985–1999) shows a clear improvement, with the proportion of lakes that were acidifying changing from 24 to 7% and with the proportion of lakes that were recovering changing from 16 to 35%. These observations suggest that the recent drop in SO₄ ^2- deposition in the northeastern U.S. and eastern Canada was significant enough to allow chemical recovery for a significant proportion of Québec lakes.     

The possible association between selected sediment characteristics and the occurrence of benthic macroinvertebrates in a minimally affected river in South Africa

Forty-two families of which the vast majority associated with particles >2000?µm were found. Sediment particle sizes <2000?µm had a detrimental effect on biodiversity. The highest biodiversity was recorded at sites characterised by riffle and run habitats. Although relatively high concentrations of selected metals were present in the sediment, it was largely from geological origin and most probably not bioavailable. No significant correlation was demonstrated between variation in temperature, pH, and electrical conductivity and diversity and abundance of macroinvertebrates. Therefore, it can be concluded that, under these conditions, sediment particle size and biotope availability played a decisive role on the distribution and abundance of macroinvertebrate taxa.     

Seasonal variation in the white muscle biochemical composition of deep-sea macrourids in the North-east Atlantic

The peculiar limpet-like morphology of the genus Colobocentrotus is unique among the regular echinoids. This shape has been interpreted as an adaptation to life in areas of extreme wave exposure. In this study the attachment strength of C. atratus is compared with that of three sympatric species, Echinometra mathaei, Heterocentrotus trigonarius and Stomopneustes variolaris, which have more typical echinoid morphology and live in different microhabitats. For each species, the adhesion of individual sea urchins was measured as well as the tenacity of single tube foot and the mechanical properties of the tube foot stems. Colobocentrotus always presented the highest measured values, although not always significantly different from those of the other species. Of the mechanical properties of the stem measured, the stem extensibility was the only property that was significantly different among species. In general the stems of all the species studied became more extensible and more difficult to break with increasing strain rate, providing an adaptative advantage to the sea urchin when subjected to rapid loads such as waves. In terms of single tube foot tenacity, C. atratus tube feet attached with a tenacity (0.54 MPa) two times higher than the one of E. mathaei, H. trigonarius and S. variolaris (0.21–0.25 MPa). Individual sea urchins of the four species, however, attached with a similar strength (0.2–0.26 MPa). The calculation of safety factors showed that it is the very high number of adoral tube feet of C. atratus and not the overall shape of the animal that allows this species to withstand very high water velocities. However, C. atratus streamlined morphology may be a functional adaptation to reduce the impact of other hydrodynamic forces (such as wave impingement forces) or to cope with other selective environmental stresses (such as dessication), and thus to inhabit extremely exposed areas of the intertidal.     

Potential direct fitness consequences of ornament-based mate choice in a butterfly

Female mate choice has been shown to provide direct mating benefits in several animal groups. In butterflies, for which there are increasing reports of fine-scale color-based mate choice, the evolutionary benefits that accrue from such mating biases, if any, are largely unknown. We addressed this issue in the butterfly Colias eurytheme, a species in which females choose mates on the basis of iridescent ultraviolet (UV) wing ornamentation and in which males donate reproductively beneficial nuptial gifts. In the first experiment, we assessed the mass of gifts donated to 77 virgin females by males sampled directly from a field encounter site. Despite large variance in the male adult phenotype and ejaculate, no single aspect of dorsal wing coloration, including UV brightness, chroma, or hue, was related to ejaculate mass. There was, however, an interesting interaction between the effects of male body size and copula duration upon ejaculate mass, with size scaling positively with ejaculate mass among males involved in shorter copulations (those lasting <70 min) but negatively among males in longer copulations. In the second experiment, we assessed the lifetime fecundity, fertility, and longevity of 85 females mated under similar circumstances to free-flying wild males. Although several wing color parameters proved subtly informative in more sophisticated multivariable models, no model predicted more than about 20% of the variation in any single female fitness parameter. The duration of copulation, which ranged from 35 min to over 16 h and which carries putative costs for females, was, again, only very weakly predicted by male wing color parameters (i.e., R ² = 0.089). Given the overall minor predictive power of male wing coloration in general and of UV brightness in particular, our results do not strongly support the hypothesis that female C. eurytheme prefer bright UV males to obtain direct benefits or to minimize the costs associated with lengthy copulations.     

Managing Sustainable Development Conflicts: The Impact of Stakeholders in Small-Scale Hydropower Schemes

The growing importance of the environment and its management has simultaneously emphasized the benefits of hydroelectric power and its environmental costs. In a changing policy climate, giving importance to renewable energy development and environmental protection, conflict potential between stakeholders is considerable. Navigation of conflict determines the scheme constructed, making sustainable hydropower a function of human choice. To meet the needs of practitioners, greater understanding of stakeholder conflict is needed. This paper presents an approach to illustrate the challenges that face small-scale hydropower development as perceived by the stakeholders involved, and how they influence decision-making. Using Gordleton Mill, Hampshire (UK), as an illustrative case, soft systems methodology, a systems modeling approach, was adopted. Through individual interviews, a range of problems were identified and conceptually modeled. Stakeholder bias towards favoring economic appraisal over intangible social and environmental aspects was identified; costs appeared more influential than profit. Conceptual evaluation of the requirements to meet a stakeholder-approved solution suggested a complex linear systems approach, considerably different from the real-life situation. The stakeholders introduced bias to problem definition by transferring self-perceived issues onto the project owner. Application of soft systems methodology caused a shift in project goals away from further investigation towards consideration of project suitability. The challenge of sustainable hydropower is global, with a need to balance environmental, economic, and social concerns. It is clear that in this type of conflict, an individual can significantly influence outcomes; highlighting the need for more structured approaches to deal with stakeholder conflicts in sustainable hydropower development.     

Phthalates and the aquatic environment: Part II The bioconcentration and depuration of di-2-ethylhexyl phthalate (DEHP) and di-isodecyl phthalate (DIDP) in mussels (Mytilus edulis)

Mussels ($\text{Mytilus edulis}$) were exposed to di-2-ethylhexyl phthalate (DEHP) and to di-isodecyl phthalate (DIDP) over a period of 28 days. The bioconcentration factor (BCF) as measured by ¹⁴C analysis, reached estimated plateau levels corresponding to mean BCF values of approximately 2500 and 3500 for the DEHP and DIDP respectively. The mussels were then held in clean seawater for a further 14 days and ¹⁴C analysis showed a depuration half-life of approximately 3.5 days for both phthalates. During the whole 42 days of the experiment general observations on the health of the animals showed no evidence of any adverse effects.