While seed-propagated crops have contributed many evolutionary insights, evolutionary biologists have often neglected clonally propagated crops. We argue that widespread notions about their evolution ...under domestication are oversimplified, and that they offer rich material for evolutionary studies. The diversity of their wild ancestors, the diverse ecologies of the crop populations themselves, and the intricate mix of selection pressures, acting not only on the parts harvested but also on the parts used by humans to make clonal propagules, result in complex and diverse evolutionary trajectories under domestication. We examine why farmers propagate some plants clonally, and discuss the evolutionary dynamics of sexual reproduction in clonal crops. We explore how their mixed clonal/sexual reproductive systems function, based on the sole example studied in detail, cassava (Manihot esculenta). Biotechnology is now expanding the number of clonal crops, continuing the 10 000-yr-old trend to increase crop yields by propagating elite genotypes. In an era of rapid global change, it is more important than ever to understand how the adaptive potential of clonal crops can be maintained. A key component of strategies for preserving this adaptive potential is the maintenance of mixed clonal/sexual systems, which can be achieved by encouraging and valuing farmer knowledge about the sexual reproductive biology of their clonal crops.
Despite growing concern over consequences of global changes, we still know little about potential interactive effects of anthropogenic perturbations and diversity loss on the stability of local ...communities, especially for taxa other than plants. Here we analyse the relationships among landscape composition, biodiversity and community stability looking at time series of three types of communities, i.e., bats, birds and butterflies, monitored over the years by citizen science programs in France. We show that urban and intensive agricultural landscapes as well as diversity loss destabilize these communities but in different ways: while diversity loss translates into greater population synchrony, urban and intensive agricultural landscapes mainly decrease mean population stability. In addition to highlight the stabilizing effects of diversity on ecologically important but overlooked taxa, our results further reveal new pathways linking anthropogenic activities to diversity and stability.
Ecological communities are structured in part by evolutionary interactions among their members. A number of recent studies incorporating phylogenetics into community ecology have upheld the paradigm ...that competition drives ecological divergence among species of the same guild. However, the role of other interspecific interactions, in particular positive interactions such as mutualism, remains poorly explored. We characterized the ecological niche and inferred phylogenetic relationships among members of a diverse community of neotropical Müllerian mimetic butterflies. Müllerian mimicry is one of the best studied examples of mutualism, in which unpalatable species converge in wing pattern locally to advertize their toxicity to predators. We provide evidence that mutualistic interactions can drive convergence along multiple ecological axes, outweighing both phylogeny and competition in shaping community structure. Our findings imply that ecological communities are adaptively assembled to a much greater degree than commonly suspected. In addition, our results show that phenotype and ecology are strongly linked and support the idea that mimicry can cause ecological speciation through multiple cascading effects on species' biology.
Uncovering the processes that shape the architecture of interaction networks is a major challenge in ecology. Studies have consistently revealed that more closely related taxa tend to show greater ...overlap in interaction partners, fuelling the idea that interactions are phylogenetically conserved 1–8. However, local ecological processes such as exploitative or apparent competition (indirect interactions) might instead cause a decrease in overlap in interacting partners. Because of the taxonomic and geographic coarseness of existing studies 2–5, 7, the structuring effect of such processes has been overlooked. Here, we assess the relative importance of phylogeny and ecological processes in a local, highly resolved, four-level antagonistic network. Across all network levels we consistently find that phylogenetic relatedness among resource species is correlated with consumer overlap but that phylogenetic relatedness among consumer species is not or negatively correlated with resource overlap. This pervasive pattern indicates that the antagonistic network has been shaped by both phylogeny on resource range and by exploitative competition limiting resource overlap among closely related consumer species. Intriguingly, the strength of phylogenetic signal varies in a consistent way across the network levels. We discuss the generality of our findings and their implications in a changing world.
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•Related “resource” species tend to be consumed by the same “consumer” species•Related consumer species tend to consume different resource species•The strength of this pattern varies consistently across antagonistic networks•Such networks are shaped by phylogeny and exploitative competition
DNA 'barcoding' relies on a short fragment of mitochondrial DNA to infer identification of specimens. The method depends on genetic diversity being markedly lower within than between species. Closely ...related species are most likely to share genetic variation in communities where speciation rates are rapid and effective population sizes are large, such that coalescence times are long. We assessed the applicability of DNA barcoding (here the 5′ half of the cytochrome c oxidase I) to a diverse community of butterflies from the upper Amazon, using a group with a well-established morphological taxonomy to serve as a reference. Only 77% of species could be accurately identified using the barcode data, a figure that dropped to 68% in species represented in the analyses by more than one geographical race and at least one congener. The use of additional mitochondrial sequence data hardly improved species identification, while a fragment of a nuclear gene resolved issues in some of the problematic species. We acknowledge the utility of barcodes when morphological characters are ambiguous or unknown, but we also recommend the addition of nuclear sequence data, and caution that species-level identification rates might be lower in the most diverse habitats of our planet.
Müllerian mimicry is a positive interspecific interaction, whereby co-occurring defended prey species share a common aposematic signal. In Lepidoptera, aposematic species typically harbour ...conspicuous opaque wing colour patterns with convergent optical properties among co-mimetic species. Surprisingly, some aposematic mimetic species have partially transparent wings, raising the questions of whether optical properties of transparent patches are also convergent, and of how transparency is achieved. Here, we conducted a comparative study of wing optics, micro and nanostructures in neotropical mimetic clearwing Lepidoptera, using spectrophotometry and microscopy imaging. We show that transparency, as perceived by predators, is convergent among co-mimics in some mimicry rings. Underlying micro- and nanostructures are also sometimes convergent despite a large structural diversity. We reveal that while transparency is primarily produced by microstructure modifications, nanostructures largely influence light transmission, potentially enabling additional fine-tuning in transmission properties. This study shows that transparency might not only enable camouflage but can also be part of aposematic signals.
Male ithomiine butterflies (Nymphalidae: Danainae) have hairpencils on the forewings (i.e., androconia) that disseminate semiochemicals during courtship. While most ithomiines are known to contain ...derivatives of pyrrolizidine alkaloids, dihydropyrrolizines, or γ-lactones in these androconia, here we report on a new class of fatty acid esters identified in two subspecies,
and
The major components were identified as isoprenyl (3-methyl-3-butenyl) (
)-3-acetoxy-11-octadecenoate, isoprenyl (
)-3-acetoxy-13-octadecenoate (
) and isoprenyl 3-acetoxyoctadecanoate (
) by GC/MS and GC/IR analyses, microderivatizations, and synthesis of representative compounds. The absolute configuration of
was determined to be
. The two subspecies differed not only in the composition of the ester bouquet, but also in the composition of more volatile androconial constituents. While some individuals of
contained ithomiolide A (
), a pyrrolizidine alkaloid derived γ-lactone,
carried the sesquiterpene α-elemol (
) in the androconia. These differences might be important for the reproductive isolation of the two subspecies, in line with previously reported low gene exchange between the two species in regions where they co-occur. Furthermore, the occurrence of positional isomers of unsaturated fatty acid derivatives indicates activity of two different desaturases within these butterflies, Δ9 and Δ11, which has not been reported before in male Lepidoptera.
Advertising escape ability could reduce predatory attacks. However, the effectiveness of certain phenotypic cues (e.g., color, shape, and size) in signaling evasiveness is still unknown. ...Understanding the role of such signals in driving predator learning is important to infer the evolutionary mechanisms leading to convergent evasiveness signals among prey species (i.e., evasive mimicry). We aim to understand the role of the color pattern (white patches on dark background) and morphology (extended butterfly hindwings) in driving learning and avoidance of escaping prey by surrogate avian predators, the European blue tit. These cues are common in butterflies and have been suspected to advertise escape ability in nature. We use dummy butterflies harboring shape and color patterns commonly found in skippers (family Hesperiidae). The prey models displayed the studied phenotypical cues (hindwing tails and white bands) in factorial combinations, and we tested whether those cues were learned as evasive signals and were generalised to different phenotypes. Our results suggest that hindwing tails and white bands can be associated with prey evasiveness. In addition, wild blue tits might learn and avoid attacking prey models bearing the studied phenotypic cues. Although blue tits seem to have an initial preference for the phenotype consisting of white patches and hindwing tails, the probability of attacking it was substantially reduced once the cues were associated with escaping ability. This suggests that the same morphological cues might be interchangeable as preference/avoidance signals. Further investigation of the salience of hindwing tails vs. white bands as cues for escaping ability, revealed that predators can associate both color pattern and shape to the difficulty of capture, and possibly generalize their aversion to other prey harboring those cues. More studies with larger sample sizes are needed to confirm this trend. Altogether, our results highlight the hitherto overlooked role of shape (butterfly hindwing tails) for signaling prey unprofitability.
Islands are bounded areas where high endemism is explained either by allopatric speciation through the fragmentation of the limited amount of space available, or by sympatric speciation and ...accumulation of daughter species. Most empirical evidence point out the dominant action of allopatric speciation. We evaluate this general view by looking at a case study where sympatric speciation is suspected. We analyse the mode, tempo and geography of speciation in Agnotecous, a cricket genus endemic to New Caledonia showing a generalized pattern of sympatry between species making sympatric speciation plausible. We obtained five mitochondrial and five nuclear markers (6.8 kb) from 37 taxa corresponding to 17 of the 21 known extant species of Agnotecous, and including several localities per species, and we conducted phylogenetic and dating analyses. Our results suggest that the diversification of Agnotecous occurred mostly through allopatric speciation in the last 10 Myr. Highly microendemic species are the most recent ones (<2 Myr) and current sympatry is due to secondary range expansion after allopatric speciation. Species distribution should then be viewed as a highly dynamic process and extreme microendemism only as a temporary situation. We discuss these results considering the influence of climatic changes combined with intricate soil diversity and mountain topography. A complex interplay between these factors could have permitted repeated speciation events and range expansion.
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