中国中生代昆虫化石研究新进展

回顾了1990年以来中国中生代昆虫化石研究的新进展,简述了我国学者在古昆虫分类学、昆虫内部形态学、昆虫系统学、古生态学、昆虫生物地层学、昆虫区系的历史演变、生物古地理学、昆虫与植物的关系等8个方面取得的突出贡献,并给出了我国发现的世界最低层位昆虫科级类群表。     

Chronostratigraphic accuracy of Ordovician ecostratigraphic correlation

Six stratigraphic sections along a 34 km transect down a Middle Ordovician depth gradient (Trenton Group, New York) were ecostratigraphically correlated to 10⁵ year accuracy by pairwise statistical cross-correlation of curves describing each section's depth history in terms of the distribution of fossil marine benthic communities along the gradient. This accuracy is about an order of magnitude greater than that of ordinary biostratigraphic correlation in the sequence, and it is attained even in correlating between very different biofacies. New ecostratigraphic methods illustrated here promise comparable improvements in analyzing many stratigraphic sequences.     

The significance of ecostratigraphy and need for biostratigraphic hierarchy in stratigraphic nomenclature

It is proposed that the lithostratigraphic, biostratigraphic and chronostratigraphic categories currently recognized in the International Stratigraphic Guide should be expanded by an additional category, provisionally termed ecostratigraphy. This category would incorporate fossil subcommunities, communities, faunal and floral provinces, and biomes, to provide an ecologic counterpart to lithostratigraphy, and would help bridge the categories of lithostratigraphy and biostratigraphy. It is also suggested that a hierarchy of terms in biostratigraphy would be useful, with formal recognition of subzones and superzones. Subzones may be defined as 'zones within zones', or short-lived biologic events in which one or a few species dominated communities, without permanently changing the benthos in the marine world. They therefore are equivalent in rank to fossil communities. Superzones are defined as correlative zones. If superzones were to be matched with substages (in biologic but not lithologic content), we would have a natural link between biostratigraphy and chronostratigraphy.     

Evolutionary theory: The current state

Modern problems for the theory of evolution in Russia are only partly related to domestic realities (a legacy of the 1990s, changing priorities of education, and the clericalization of the society). The main drawback comes from the acceptance of a physicalist paradigm, in which testing evolutionary hypotheses is reduced to testing predictions derived from processes working at lower levels. Hypotheses are no longer tested by direct observation of the real world, which has somehow ceased to be regarded as a source of proof. Instead, hypotheses are thought to be correct if they are supported by more readily understood patterns at lower (molecular or genetic) levels. This substitution may explain the poor support for the epigenetic theory of evolution, although it agrees with observations much better than the currently dominant theoretical concepts.     

Evolution in metacommunities

A metacommunity can be defined as a set of communities that are linked by migration, and extinction and recolonization. In metacommunities, evolution can occur not only by processes that occur within communities such as drift and individual selection, but also by among-community processes, such as divergent selection owing to random differences among communities in species composition, and group and community-level selection. The effect of these among-community-level processes depends on the pattern of migration among communities. Migrating units may be individuals (migrant pool model), groups of individuals (single-species propagule pool model) or multi-species associations (multi-species propagule pool model). The most interesting case is the multi-species propagule pool model. Although this pattern of migration may a priori seem rare, it becomes more plausible in small well-defined 'communities' such as symbiotic associations between two or a few species. Theoretical models and experimental studies show that community selection is potentially an effective evolutionary force. Such evolution can occur either through genetic changes within species or through changes in the species composition of the communities. Although laboratory studies show that community selection can be important, little is known about how important it is in natural populations.     

Unidirectional flow in lizard lungs: a paradigm shift in our understanding of lung evolution in Diapsida

Conventional wisdom has held that unidirectional pulmonary airflow is unique to birds and is an adaption enabling high rates of gas exchange, essential for sustaining flight as well as an endothermic metabolism. Recent visualizations and measurements of flow in the lungs of monitor and iguanid lizards show a bird-like pattern of unidirectional flow in these lineages. These findings call for a paradigm shift in our understanding of lung evolution in diapsids. This pattern of flow is not unique to birds. It is much older than previously believed, and it may be advantageous to the low-energy lifestyles typical of ectothermic animals.     

Competition theory,evolution, and the concept of an ecological niche

This article examines some of the main tenets of competition theory in light of the theory of evolution and the concept of an ecological niche. The principle of competitive exclusion and the related assumption that communities exist at competitive equilibrium - fundamental parts of many competition theories and models - may be violated if non-equilibrium conditions exist in natural communities or are incorporated into competition models. Furthermore, these two basic tenets of competition theory are not compatible with the theory of evolution. Variation in ecologically significant environmental factors and non-equilibrium in population numbers should occur in most natural communities, and such changes have important effects on community relations, niche overlap, and the evolution of ecosystems. Ecologists should view competition as a process occurring within a complexdynamic system, and should be wary of theoretical positions built upon simple laboratory experiments or simplistic mathematical models.In considering the relationship between niche overlap and competition, niche overlap should not be taken as a sufficient condition for competition; many factors may prevent or diminish competition between populations with similar resource utilization patterns. The typically opposing forces of intraspecific and interspecific competition need to be simultaneously considered, for it is the balance between them that in large part determines niche boundaries.     

Correlated evolution between male ejaculate allocation and female remating behaviour in seed beetles (Bruchidae)

Sperm competition theory suggests that female remating rate determines the selective regime that dictates the evolution of male ejaculate allocation. To test for correlated evolution between female remating behaviour and male ejaculate traits, we subjected detailed experimental data on female and male reproductive traits in seven-seed beetle species to phylogenetic comparative analyses. The evolution of a larger first ejaculate was positively correlated with the evolution of a more rapid decline in ejaculate size over successive matings. Further, as predicted by theory, an increase in female remating rate correlated with the evolution of larger male testes but smaller ejaculates. However, an increase in female remating was associated with the evolution of a less even allocation of ejaculate resources over successive matings, contrary to classic sperm competition theory. We failed to find any evidence for coevolution between the pattern of male ejaculate allocation and variation in female quality and we conclude that some patterns of correlated evolution are congruent with current theory, whereas some are not. We suggest that this may reflect the fact that much sperm competition theory does not fully incorporate other factors that may affect the evolution of male and female traits, such as trade-offs between ejaculate expenditure and other competing demands and the evolution of resource acquisition.     

A call for a new paradigm of island biogeography

MacArthur and Wilson’s equilibrium theory of island biogeography quickly became the paradigm of the field in the 1960s and has strongly influenced this and other disciplines of ecology and conservation biology for the past three decades. Recently, however, a growing number of ecologists have begun to question whether the theory remains a useful paradigm for modern ecology. We now have a much better appreciation for the complexity of nature and we study patterns that span a very broad range in spatial, temporal and ecological scales. At such scales, assumptions that communities are in equilibrium, that species, islands and intervening landscapes or seascapes are equivalent or homogeneous with respect to factors influencing immigration and extinction, and that in situ speciation can be overlooked become very tenuous. With this in mind, this and other papers of this special feature discuss the principal, conceptual shortcomings of the equilibrium theory and offer some modifications or alternatives to the theory that we hope will eventually lead to a more comprehensive understanding of the forces structuring insular communities.     

Editor's column: Ecostratigraphy

[Anders Martinsson:] Editor's column: Ecostratigraphy.
The natural development of biostratigraphy is toward ecostratigraphy , i.e. the correlation of fossil ecosystems and their arrangement in a geochronological framework. This stage is not easily attainable and provides far-reaching systematical and ecological knowledge of the organisms and communities involved. Hence, considerable ecostratigraphical success is hitherto only to be reported from the Quaternary, but the development should be guided towards similar knowledge of earlier intervals of the Phanerozoic.     

Saturating effects of species diversity on life-history evolution in bacteria

Species interactions can play a major role in shaping evolution in new environments. In theory, species interactions can either stimulate evolution by promoting coevolution or inhibit evolution by constraining ecological opportunity. The relative strength of these effects should vary as species richness increases, and yet there has been little evidence for evolution of component species in communities. We evolved bacterial microcosms containing between 1 and 12 species in three different environments. Growth rates and yields of isolates that evolved in communities were lower than those that evolved in monocultures, consistent with recent theory that competition constrains species to specialize on narrower sets of resources. This effect saturated or reversed at higher levels of richness, consistent with theory that directional effects of species interactions should weaken in more diverse communities. Species varied considerably, however, in their responses to both environment and richness levels. Mechanistic models and experiments are now needed to understand and predict joint evolutionary dynamics of species in diverse communities.     

Influence of evolution on the stability of ecological communities

In randomly assembled communities, diversity is known to have a destabilizing effect. Evolution may affect this result, but our theoretical knowledge of its role is mostly limited to models of small food webs. In the present article, I introduce evolution in a two-species Lotka-Volterra model in which I vary the interaction type and the cost constraining evolution. Regardless of the cost type, evolution tends to stabilize the dynamics more often in trophic interactions than for mutualism or competition. I then use simulations to study the effect of evolution in larger communities that contain all interaction types. Results suggest that evolution usually stabilizes the dynamics. This stabilizing effect is stronger when evolution affects trophic interactions, but happens for all interaction types. Stabilization decreases with diversity and evolution becomes destabilizing in very diverse communities. This suggests that evolution may not counteract the destabilizing effect of diversity observed in random communities.     

Stratigraphic interpretation of the Kulu Formation (Early Miocene, Rusinga Island, Kenya) and its implications for primate evolution

Early Miocene fossils from Rusinga Island, Kenya, provide some of the best evidence for catarrhine evolution and diversification, and, together with more than eighty-five other mammalian species, form an important comparative reference for understanding faunal succession in East Africa. While there is consensus over the stratigraphic position of most of Rusinga's volcaniclastic deposits, the lacustrine Kulu Formation has been placed in various parts of the geological sequence by different researchers. To resolve this discrepancy, we conducted detailed geological analyses which indicate that the Kulu Formation was formed in the Early Miocene during a period of volcanic inactivity and subsidence following the early, mainly explosive hyper-alkaline phase of the Kisingiri complex and prior to the final eruptions of nephelinitic lavas. The underlying Hiwegi and older formations were locally deformed and deeply eroded before sedimentation began in the Kulu basin, so that the Kulu sediments may be significantly younger than the 17.8 Ma Hiwegi Formation and not much older than the overlying Kiangata Agglomerata-Lunene Lava series, loosely dated to ca. 15 Ma. The overall similarities between Kulu and Hiwegi faunas imply long-term ecological stability in this region. Our stratigraphic interpretation suggests that the Kulu fauna is contemporaneous with faunas from West Turkana, implying that differences between these assemblages—particularly in the primate communities—reflect paleobiogeographic and/or paleocological differences. Finally, the position of the Kulu Formation restricts the time frame during which the substantial faunal turnover seen in the differences between the primate and mammalian communities of Rusinga and Maboko Islands could have occurred.     

Studying Cultural Evolution at the Tips: Human Cross-cultural Ecology

While human genetic variation is limited due to a bottleneck on the origin of the species ～200 kya, cultural traits can change more rapidly, and may do so in response to the variation in human habitats. Does cultural diversification simulate a natural experiment in evolution much like biodiversity so that cultural divergences and convergences can be interpreted in terms of the differences and similarities of local environments? Or is cultural diversity simply the result of human behavioral flexibility? Although the majority of cultural data comes from the tips of the hominin phylogeny, anthropologists can follow the example of evolutionary ecologists, who often compare the endpoints of phylogenies when that is all that is available. This article compares 97 contemporary indigenous language communities from around the world, and 24 of their cultural traditions, to help determine whether human cultures and their cultural traits are proportionately dispersed, as predicted by the neutral theory of biodiversity, or whether they show non-proportionalities that could be explained with evolutionary reasoning.     

Functional and phylogenetic approaches reveal the evolution of diversity in a hyper diverse biota

Ant communities in tropical forests may be governed by varying assembly mechanisms, depending on the particular habitat investigated. We compared phylogenetic diversity and structure across two forest biomes (dry and humid) and two vertical layers (arboreal and terricolous) in ant communities in Madagascar, and assessed the influence of invasive species on this community structure. We estimated phylogenetic signal and correlated evolution for habitat and several functional traits and tested for conservatism in relevant functional and habitat traits. Ancestral states were reconstructed to illuminate the evolution of habitat traits. All analyses utilized phylogenies estimated from newly generated data from three nuclear markers for 290 Malagasy ant taxa. Dry forests, although lower in species richness, were found to support equally high lineage diversity as humid forests. In contrast, phylogenetic diversity was much lower in arboreal than in terricolous communities. We observed significant phylogenetic clustering in the combined humid forest and in the arboreal–humid, arboreal–dry and terricolous–humid communities, whereas the combined dry forest community was overdispersed. Among ant communities in Madagascar, overdispersion and competition therefore may be more prevalent in dry forest, and habitat filtering may be more dominant in humid forest. Excluding invasive ant species had little overall effect on community structure. All investigated traits showed low to intermediate conservatism; strong support for correlated evolution was found for increased eye size and an arboreal lifestyle. Habitat transitions from humid to dry and from terricolous to arboreal occurred more frequently, and ancestors of most lineages were predicted to be terricolous or humid‐forest adapted. We conclude that most Malagasy ant clades first colonized humid forests and subsequently transitioned into dry forests, indicating that previous hypotheses on the evolution of Madagascar's hyperdiverse biota may not apply to ants and other arthropods.     

Defining climate's role in ecosystem evolution: Clues from late quaternary mammals

Mammalian communities alter their taxonomic composition through time as the species composing them change their biogeographic range, become extinct, or evolve into new species. When taxonomic compositions change through these processes, inevitably the links between taxa and communities change too, resulting in evolution from one ecosystem into the next. Late Quaternary examples suggest that on a timescale encompassing a few thousand to a few hundred thousand years (the “multi‐millennial timescale"), climatic change is perhaps the most important driver of ecosystem evolution because it periodically forces biogeographic changes and extinction. Climatic change over this timescale, which essentially slips between “geological time”; and “ecological time”;, is not very closely in phase with population‐level evolution of a species analyzed for this study, the meadow vole Microtus pennsylvanicus; therefore climatic oscillations on the multi‐millennial timescale may not stimulate speciation much. Instead, speciation may contribute to ecosystem evolution independent of climatic change and over a longer time scale.     

Faunal response to sea‐level and climate change in a short‐lived seaway: Jurassic of the Western Interior,USA

Understanding how regional ecosystems respond to sea‐level and environmental perturbations is a main challenge in palaeoecology. Here we use quantitative abundance estimates, integrated within a sequence stratigraphic and environmental framework, to reconstruct benthic community changes through the 13 myr history of the Jurassic Sundance Seaway in the western United States. Sundance Seaway communities are notable for their low richness and high dominance relative to most areas globally in the Jurassic, and this probably reflects steep temperature and salinity gradients along the 2000 km length of the Seaway that hindered colonization of species from the open ocean. Ordination of samples shows a main turnover event at the Middle–Upper Jurassic transition, which coincided with a shift from carbonate to siliciclastic depositional systems in the Seaway, probably initiated by northward drift from subtropical latitudes to more humid temperate latitudes, and possibly global cooling. Turnover was not uniform across the onshore–offshore gradient, but was higher in offshore environments. The higher resilience of onshore communities to third‐order sea‐level fluctuations and to the change from a carbonate to a siliciclastic system was driven by a few abundant eurytopic species that persisted from the opening to the closing of the Seaway. Lower stability in offshore facies was instead controlled by the presence of more volatile stenotopic species. Such increased onshore stability in community composition contrasts with the well‐documented onshore increase in taxonomic turnover rates, and this study underscores how ecological analyses of relative abundance may contrast with taxonomically based analyses. We also demonstrate the importance of a stratigraphic palaeobiological approach to reconstructing the links between environmental and faunal gradients, and how their evolution through time produces local stratigraphic changes in community composition.     

Eustatic trends in conodont diversity across the Frasnian–Famennian boundary in the stratotype area, Montagne Noire, Southern France

Trends in generic diversity of successive conodont communities are analysed in sections of different environmental settings across the Frasnian–Famennian (F–F) boundary in the stratotype area, Montagne Noire, France. The evolution of conodont biofacies and abundances matches the overall pattern already observed in many sections elsewhere in the world and supports the interpretation of an important eustatic sea-level fall during the Upper Kellwasser event. The change from late Frasnian deep-water palmatolepid–polygnathid biofacies to shallower-water polygnathid-icriodid biofacies during the Upper Kellwasser event occurred in all sections studied. The shallowing trend culminated at the end of the Kellwasser Event as indicated by the substantial increase of formerly poorly represented icriodids, whereas palmatolepids concomi-tantly diminished. This event occurred earlier on oxygenated outer platform submarine rises than in oxygen-depleted depressions. The sudden sea-level fall prior to the Frasnian–Famennian boundary was followed, at the beginning of the Famennian, by a deepening trend when palmatolepids dominated again. These changes in conodont generic associations and abundances occurred rapidly and synchronously. As a result, the stratigraphic resolution obtained with the evolution of biofacies is higher: it permits not only a more accurate location of the base of the Upper Kellwasser event in environments where it cannot be distinguished lithologically, but it also allows the recognition of intrazonal gaps.     

CAN PARALLEL DIVERSIFICATION OCCUR IN SYMPATRY? REPEATED PATTERNS OF BODY‐SIZE EVOLUTION IN COEXISTING CLADES OF NORTH AMERICAN SALAMANDERS

A classic paradigm in evolutionary biology is that geographically isolated clades inhabiting similar selective regimes will diversify to create similar sets of phenotypes in different locations (e.g., similar stickleback species in different lakes, similar Anolis ecomorphs on different islands). Such parallel radiations are not generally expected to occur in sympatry because the available niche space would be filled by whichever clade is diversified first. Here, we document a very different pattern, the parallel evolution of similar body-size morphs in three sympatric clades of plethodontid salamanders ( Desmognathus, Plethodon, Spelerpinae) in eastern North America. Using a comprehensive, time-calibrated phylogeny of North American plethodontids from nuclear and mitochondrial DNA sequences, we show that these three clades have undergone replicated patterns of evolution in body size and that this parallel diversification occurred in broad-scale sympatry. At the local scale, we find that coexisting species from these clades are more similar in body size than expected under a null model in which species are randomly assembled into communities. These patterns are particularly surprising in that competition is known to be important in driving phenotypic diversification and limiting local coexistence of similar-sized species within these clades. Although parallel diversification of sympatric clades may seem counterintuitive, we discuss several ecological and evolutionary factors that may allow the phenomenon to occur.