Value of long‐term ecological studies

Long‐term ecological studies are critical for providing key insights in ecology, environmental change, natural resource management and biodiversity conservation. In this paper, we briefly discuss five key values of such studies. These are: (1) quantifying ecological responses to drivers of ecosystem change; (2) understanding complex ecosystem processes that occur over prolonged periods; (3) providing core ecological data that may be used to develop theoretical ecological models and to parameterize and validate simulation models; (4) acting as platforms for collaborative studies, thus promoting multidisciplinary research; and (5) providing data and understanding at scales relevant to management, and hence critically supporting evidence‐based policy, decision making and the management of ecosystems. We suggest that the ecological research community needs to put higher priority on communicating the benefits of long‐term ecological studies to resource managers, policy makers and the general public. Long‐term research will be especially important for tackling large‐scale emerging problems confronting humanity such as resource management for a rapidly increasing human population, mass species extinction, and climate change detection, mitigation and adaptation. While some ecologically relevant, long‐term data sets are now becoming more generally available, these are exceptions. This deficiency occurs because ecological studies can be difficult to maintain for long periods as they exceed the length of government administrations and funding cycles. We argue that the ecological research community will need to coordinate ongoing efforts in an open and collaborative way, to ensure that discoverable long‐term ecological studies do not become a long‐term deficiency. It is important to maintain publishing outlets for empirical field‐based ecology, while simultaneously developing new systems of recognition that reward ecologists for the use and collaborative sharing of their long‐term data sets. Funding schemes must be re‐crafted to emphasize collaborative partnerships between field‐based ecologists, theoreticians and modellers, and to provide financial support that is committed over commensurate time frames.     

Recent and recurrent polyploidy in Tragopogon (Asteraceae): cytogenetic, genomic and genetic comparisons

Tragopogon mirus Ownbey and T. miscellus Ownbey are allopolyploids that formed repeatedly during the past 80 years following the introduction of three diploids (T. dubius Scop., T. pratensis L. and T. porrifolius L.) from Europe to western North America. These polyploid species of known parentage are useful for studying the consequences of recent and recurrent polyploidization. We summarize recent analyses of the cytogenetic, genomic and genetic consequences of polyploidy in Tragopogon. Analyses of rDNA ITS (internal transcribed spacer) + ETS (external transcribed spacer) sequence data indicate that the parental diploids are phylogenetically well separated within Tragopogon (a genus of perhaps 150 species), in agreement with isozymic and cpDNA data. Using Southern blot and cloning experiments on tissue from early herbarium collections of T. mirus and T. miscellus (from 1949) to represent the rDNA repeat condition closer to the time of polyploidization than samples collected today, we have demonstrated concerted evolution of rDNA. Concerted evolution is ongoing, but has not proceeded to completion in any polyploid population examined; rDNA repeats of the diploid T. dubius are typically lost or converted in both allopolyploids, including populations of independent origin. Molecular cytogenetic studies employing rDNA probes, as well as centromeric and subtelomeric repeats isolated from Tragopogon, distinguished all chromosomes among the diploid progenitors (2n = 12). The diploid chromosome complements are additive in both allopolyploids (2n = 24); there is no evidence of major chromosomal rearrangements in populations of either T. mirus or T. miscellus. cDNA‐AFLP display revealed differences in gene expression between T. miscellus and its diploid parents, as well as between populations of T. miscellus of reciprocal origin. Approximately 5% of the genes examined in the allopolyploid populations have been silenced, and an additional 4% exhibit novel gene expression relative to their diploid parents. Some of the differences in gene expression represent maternal or paternal effects. Multiple origins of a polyploid species not only affect patterns of genetic variation in natural populations, but also contribute to differential patterns of gene expression and may therefore play a major role in the long‐term evolution of polyploids. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 82 , 485–501.     

Catchment land-use, macroinvertebrates and detritus processing in headwater streams: taxonomic richness versus function

1. We used a litter bag technique to assess the effect of catchment land-use (forest, wetland, agriculture, urban) on the processing of red maple ( Acer rubrum L.) litter in 17 streams in Maine, U.S.A. Litter processing by fungi was predicted to increase with nutrient concentrations along a gradient of land use, from relatively unmodified to highly modified. Litter processing by litter-shredding macroinvertebrates was predicted to decline along this gradient because of a decline in their taxonomic richness and biomass.
2. Land use was associated with the anticipated gradient in nutrient and macroinvertebrate attributes, and a significant relationship was found between land use and nitrate concentration. There was, however, no significant relationship between land use and soluble reactive phosphorus (SRP) concentration. Similarly, shredder taxonomic richness was significantly related to land use type, whereas shredder biomass showed no significant relationship to land use.
3. Attributes of the shredder assemblage structure and nutrient concentrations were both strong determinants of litter processing. Increasing biomass and taxonomic richness of shredders was significantly related to increasing rates of litter mass loss. Increasing concentrations of nitrate and SRP were significantly related to increasing rates of litter softening below threshold concentrations (approximately 0.20 mg NO₃-N L^–1 and 5 μg SRP L^–1).
4. The potentially additive effects of nitrate and SRP concentrations or shredder richness and biomass on litter processing rates were confounded by the lack of significant correlation between these pairs of variables. Consequently, rates of litter processing (as rates of softening or mass loss) did not vary systematically among different land use regimes.     

Deforestation causes increased dissolved silicate losses in the Hubbard Brook Experimental Forest

Globally significant increases in the riverine delivery of nutrients and suspended particulate matter have occurred with deforestation. We report here significant increases in streamwater transport of dissolved silicate (DSi) following experimental forest harvesting at the Hubbard Brook Experimental Forest, NH, USA. The magnitude of the streamwater response varied with the type of disturbance with the highest DSi export fluxes occurring in the manipulations that left the most plant materials on the soil surface and disturbed the soil surface least. No measurable loss of amorphous silica (ASi) was detected from the soil profile; however, ASi was redistributed within the soil profile after forest disturbance. Mass‐balance calculations demonstrate that some fraction of the DSi exported must come from dissolution of ASi and export as DSi. Land clearance and the development of agriculture may result in an enhanced flux of DSi coupled with enhanced erosion losses of ASi contained in phytoliths.     

The ghost of hybrids past: fixation of arctic charr (Salvelinus alpinus) mitochondrial DNA in an introgressed population of lake trout (S. namaycush)

Complete fixation of arctic charr ( Salvelinus alpinus ) mitochondrial DNA (mtDNA) was observed in a southern Québec population of lake trout ( S. namaycush ). This introgressed population otherwise appeared to be normal with regard to lake trout morphology and three species-diagnostic microsatellite loci. Arctic charr do not occur in the area, suggesting that the hybridization event was prehistoric. Of several possible hypotheses, the most plausible explanation for this aberrant population is that hybridization occurred in situ soon after deglaciation, with repeated backcrossing of hybrids with lake trout. Fixation of S. alpinus mtDNA in the population may have occurred either by chance (drift) or selection, although indirect evidence and data from similarly introgressed brook trout ( S. fontinalis ) populations in the region suggest that selection favouring the S. alpinus mitochondrial type and/or associated nuclear genes may have been involved.     

Is the distribution of Starlings Sturnus vulgaris within roosts determined by competition?

Observations were made in five aviaries to determine the role of competition in roost site selection by captive Starlings Sturnus vulgaris. Their behaviour in selecting perches in a simple roost "tree" indicated that (1) a dominance hierarchy exists in birds selecting roosting locations, (2) the roost positions occupied are determined through competition, (3) higher and inner roost positions are preferred over others and (4) dominant Starlings tend to occupy these most preferred positions.     

Ecologically relevant cryptic species in the highly polymorphic Amazonian butterfly Mechanitis mazaeus s.l. (Lepidoptera: Nymphalidae; Ithomiini)

The understanding of mimicry has relied on a strong biosystematic framework ever since early naturalists first recognized this textbook example of natural selection. We follow in this tradition, applying new biosystematics information to resolve problems in an especially difficult genus of tropical butterflies. Mechanitis species are important components of Neotropical mimetic communities. However, their colour pattern variability has presented challenges for systematists, and has made it difficult to study the very mimicry they so nicely illustrate. The South American Mechanitis mazaeus and relatives have remained particularly intractable. Recent systematists have recognized one highly polytypic species, whereas earlier work recognized the melanic Andean foothill races as a distinct species: Mechanitis messenoides. Recent molecular evidence suggests M. mazaeus and M. messenoides are genetically well differentiated, but evidence of morphological and ecological differences indicative of separate species was still lacking. Thus, it remains to be conclusively demonstrated whether this is an extreme case of a polymorphic mimetic species, or whether distinct co‐mimetic lineages are involved. Here we provide evidence that M. mazaeus and M. messenoides are ecologically distinct and identify consistent morphological differences in both adult and immature stages. These ecological and morphological differences are correlated with mitochondrial sequence data. In spite of some overlap in almost all traits, wing shape, adult colour pattern, and larval colour pattern differ between the two species, in addition to clutch size and larval host use in local sympatry. Although three well‐differentiated mitochondrial DNA (mtDNA) haplogroups were identified within these two species, one for M. mazaeus and two within M. messenoides, no morphological or ecological differences were found between two mtDNA haplogroups, both of which appear to belong to M. messenoides. We conclude that M. mazaeus and M. messenoides are distinct although highly polymorphic species, each with multiple sympatric co‐mimetic forms, and suggest that further work is needed to clarify the identity of other phenotypes and subspecies of Mechanitis. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 540–560.     

Evaluating female remating rates in light of spermatophore degradation in Heliconius butterflies: pupal‐mating monandry versus adult‐mating polyandry

1. Butterflies are frequently used in comparative studies of sexual selection because of their diverse mating systems. In Heliconius, the two major clades in the genus are characterised by contrasting pupal‐mating and adult‐mating strategies. Adult‐mating females are considered to be promiscuous whereas pupal‐mating females are thought to be monandrous. 2. Counting spermatophores in female Lepidoptera is a common method for assessing patterns of female remating. However, in pupal‐mating Heliconius butterflies spermatophores can become completely degraded, potentially leading to underestimation of female remating rates. 3. We qualitatively characterised the different states of spermatophore degradation, and showed that complete degradation takes approximately 3 weeks in captive‐bred H. erato females. 4. We counted spermatophores and/or assayed spermatophore degradation in > 500 Heliconius females across 28 species sampled from natural populations. Among pupal‐maters these observations yielded a few rare observations of double mating by recently eclosed females, but generally indicated a lack of rematings. In contrast, approximately 25% of sampled adult‐mating females remated at least once. 5. Using a novel statistical analysis, we estimated remating rates from patterns of spermatophore degradation or from counts stratified by age, as indicated by wing‐wear. This analysis showed no statistically significant evidence for remating for the pupal‐mating H. erato whereas significant remating rates were detected for adult‐mating species. 6. The present results support the established view of Heliconius mating systems in which pupal‐maters are largely monandrous, whereas adult‐maters are polyandrous.     

Improving biodiversity monitoring

Effective biodiversity monitoring is critical to evaluate, learn from, and ultimately improve conservation practice. Well conceived, designed and implemented monitoring of biodiversity should: (i) deliver information on trends in key aspects of biodiversity (e.g. population changes); (ii) provide early warning of problems that might otherwise be difficult or expensive to reverse; (iii) generate quantifiable evidence of conservation successes (e.g. species recovery following management) and conservation failures; (iv) highlight ways to make management more effective; and (v) provide information on return on conservation investment. The importance of effective biodiversity monitoring is widely recognized (e.g. Australian Biodiversity Strategy). Yet, while everyone thinks biodiversity monitoring is a good idea, this has not translated into a culture of sound biodiversity monitoring, or widespread use of monitoring data. We identify four barriers to more effective biodiversity monitoring in Australia. These are: (i) many conservation programmes have poorly articulated or vague objectives against which it is difficult to measure progress contributing to design and implementation problems; (ii) the case for long‐term and sustained biodiversity monitoring is often poorly developed and/or articulated; (iii) there is often a lack of appropriate institutional support, co‐ordination, and targeted funding for biodiversity monitoring; and (iv) there is often a lack of appropriate standards to guide monitoring activities and make data available from these programmes. To deal with these issues, we suggest that policy makers, resource managers and scientists better and more explicitly articulate the objectives of biodiversity monitoring and better demonstrate the case for greater investments in biodiversitymonitoring. There is an urgent need for improved institutional support for biodiversity monitoring in Australia, for improved monitoring standards, and for improved archiving of, and access to, monitoring data. We suggest that more strategic financial, institutional and intellectual investments in monitoring will lead to more efficient use of the resources available for biodiversity conservation and ultimately better conservation outcomes.