Jussi Päivinen

Ecological correlates of distribution change and range shift in butterflies

Abstract  1. In order to be effective custodians of biodiversity, one must understand what ecological characteristics predispose species to population decline, range contraction, and, eventually, to extinction.

Interactions between ecological traits and host plant type explain distribution change in noctuid moths.

The ecological traits of species determine how well a species can withstand threats to which it is exposed. If these predisposing traits can be identified, species that are most at risk of decline can be identified and an understanding of the processes behind the declines can be gained. We sought to determine how body size, specificity of larval host plant, overwintering stage, type of host plant, and the interactions of these traits are related to the distribution change in noctuid moths. We used data derived from the literature and analyzed the effects of traits both separately and simultaneously in the same model. When we analyzed the traits separately, it seemed the most important determinants of distribution change were overwintering stage and type of host plant. Nevertheless, ecological traits are often correlated and the independent effect of each trait may not be seen in analyses in which traits are analyzed separately. When we accounted for other correlated traits, the results were substantially different. Only one trait (body size), but 3 interactions, explained distribution change. This finding suggests that distribution change is not determined by 1 or 2 traits; rather, the effect of the traits depends on other interacting traits. Such complexity makes it difficult to understand the processes behind distribution changes and emphasizes the need for basic ecological knowledge of species. With such basic knowledge, a more accurate picture of the factors causing distribution changes and increasing risk of extinction might be attainable.

Species richness and regional distribution of myrmecophilous beetles.

Four major hypotheses have been put forward to explain local species richness of commensal or parasitic species. The resource distribution hypothesis predicts that regionally widespread host species are able to support higher local species richness of commensals or parasites. On the other hand, the resource size hypothesis predicts that larger hosts can support more species than smaller hosts, and comparably, the resource abundance hypothesis predicts that hosts that offer more resources are able to support more species. Finally, the resource concentration hypothesis predicts that hosts that occur in high-density patches support higher species richness. In this study, we tested the first three of the above hypotheses with myrmecophilous beetles and their host ants. In addition to species richness of myrmecophilous beetles, we also applied the above hypotheses to explain the distribution of the beetles. Our data are exclusively based on an extensive literature survey. Myrmecophilous beetles live in naturally fragmented environments composed of host ant colonies and they are exclusively dependent on ants. We found that the distribution of the host ants and the colony size of the host ants had a positive effect on both the species richness and the distribution of myrmecophilous beetles. In the same way, we found that myrmecophilous beetle species that are generalists, i.e. have more than one host ant species, and thus have more abundant resources, were more widely distributed than specialist species. Thus, we found support for the hypothesis that resource distribution, resource size and resource abundance have an effect on species richness and on the distribution of species.

Missing the rarest: is the positive interspecific abundance–distribution relationship a truly general macroecological pattern?

Lepidopterists have long acknowledged that many uncommon butterfly species can be extremely abundant in suitable locations. If this is generally true, it contradicts the general macroecological pattern of the positive interspecific relationship between abundance and distribution, i.e. locally abundant species are often geographically more widespread than locally rare species. Indeed, a negative abundance–distribution relationship has been documented for butterflies in Finland. Here we show, using the Finnish butterflies as an example, that a positive abundance–distribution relationship results if the geographically restricted species are missed, as may be the case in studies based on random or restricted sampling protocols, or in studies that are conducted over small spatial scales. In our case, the abundance–distribution relationship becomes negative when approximately 70 per cent of the species are included. This observation suggests that the abundance–distribution relationship may in fact not be linear over the entire range of distributions. This intriguing possibility combined with some taxonomic biases in the literature may undermine the generalization that for a given taxonomic assemblage there is a positive interspecific relationship between local abundance and regional distribution.

The role of power line rights-of-way as an alternative habitat for declined mire butterflies

Habitat loss is one of the greatest threats for biodiversity. In Finland, two thirds of natural mires have been drained for silviculture, which transforms open wetlands into dense forests. However, vegetation management of power line rights-of-way (ROW) maintain the drained mires as open areas. The aim of this study was to determine the effect of the power line ROW vegetation management on butterfly abundance, species richness and community structure by comparing the managed power line ROWs to unmanaged drained control sites and to natural mires. The species richness or abundance of mire butterflies did not differ between the power line ROWs and natural mires. In contrast, both species richness and abundance of butterflies was low on the unmanaged control sites. Tree canopy cover had a negative effect on mire butterflies and this is most likely related to changes in microclimate. The results indicate that the active vegetation removal in the power line ROWs maintain alternative habitats for mire butterflies; yet, the power line ROWs cannot substitute the natural mires.

On the obvious positive interspecific relationship between abundance and distribution: a reply to Blackburn and Gaston

Thomas Kuhn described normal science as ‘ … research firmly based upon one or more past scientific achievements … ’, that ‘ … does not aim at novelties of fact or theory and, when successful, finds none’ ([Kuhn 1996][1]). Kuhn divides scientific enterprise into three faces: normal

Varying Definitions of Abundance and Incomplete Assemblages Challenge the Generality of the Interspecific Abundance—Distribution Relationships

Empirical evidence does not fully support the universal nature of the positive interspecific abundance—distribution relationship. We have earlier documented a negative relationship for butterfly species in Finland, but recently our view was again challenged using a small subset of Finnish butterflies as apparent evidence. Here we scrutinize the critique and identify some general conceptual challenges in analyses of interspecific abundance—distribution relationships. We identify the common problem that the abundance—distribution studies include only a small subset of species, and thus reveal only sample characteristics, not overall patterns in complete assemblages. Small subsets of species are also unlikely to have sufficient power to reveal nonlinear relationships. Second, varying definitions of abundance, especially the practice of using a single point estimate to describe average density, further spur the empirical evidence for the abundance—distribution relationship. To get theoretically relevant results abundance and distribution must be defined and operationalised consistently; otherwise macroecology will reduce to simple documentation of ambiguous patterns and aid little in understanding the biological world.

Restoration priorities and strategies

Restoration is a tool to achieve several of the strategic targets of The Convention on Biological Diversity from 2010. Currently, there is no standard for how to set priorities for restoration. The aim of this project was to exchange knowledge between the Nordic countries and Estonia regarding experiences of restoration and priority setting with a landscape perspective. Using case examples, the project explores and discusses approaches for setting priorities, and suggests possible ways of improved approaches for prioritization. This includes how to improve Green Infrastructure and measures for protection of species and habitats in fragmented landscapes. The case examples use different approaches, and provide ideas, reflections and take-home messages to enhance future prioritization. This report show that there is a need for greater emphasis on the prioritization aspects of restoration.

The Nordic Aichi restoration project

The Convention of Biological Diversity commits the parties to halt the loss of biodiversity within 2020. For accomplishing this task, the Aichi targets have been established. Aichi target 15 aims a ...