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71.
Marissa J. Betts Glenn A. Brock John R. Paterson 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2016,49(4):478-491
Mode of preservation and method of recovery strongly influences our understanding of the life habits of extinct organisms. Bradoriid arthropods were abundant, and diverse members of early Cambrian ecosystems and most life reconstructions display these animals with the two shields of the carapace open in a ‘butterfly’ configuration. This favoured reconstruction is largely based on the abundance of ‘crack‐out’ specimens preserved in this position (e.g. Kunmingella from the early Cambrian of China). In contrast, large collections of acid processed bradoriids from the Arrowie Basin of South Australia (Cambrian Stage 3) are preserved with a narrow gape at the ventral margin or completely closed with the carapace folded along the dorsal midline. The relative abundance of conjoined, closed (or partially closed) specimens from the lower Cambrian Hawker Group succession suggests that at least some bradoriid taxa were capable of withdrawing appendages and tightly closing the shields, challenging the common view that the majority of bradoriids usually held their carapaces open in a ‘butterfly’ configuration during life. New data show that layers of the bradoriid carapace are continuous through the dorsal fold with no evidence for complex articulating structures as in ostracod hinges. The relatively pliable, sclerotized or lightly mineralized calcium phosphate composition of the carapace and the simple, flexible dorsal fold facilitated opening and closing of the shields. Despite not being closely related, ostracods share close biomechanical and ecological similarities with bradoriids. The evolution of more complex articulating hinge structures – together with well‐developed musculature – in ostracods during the Early Ordovician, may have provided more efficient means for shield articulation and movement, thus promoting the ecological success of ostracods throughout the Phanerozoic. 相似文献
72.
H. Wirta G. Várkonyi C. Rasmussen R. Kaartinen N. M. Schmidt P. D. N. Hebert M. Barták G. Blagoev H. Disney S. Ertl P. Gjelstrup D. J. Gwiazdowicz L. Huldén J. Ilmonen J. Jakovlev M. Jaschhof J. Kahanpää T. Kankaanpää P. H. Krogh R. Labbee C. Lettner V. Michelsen S. A. Nielsen T. R. Nielsen L. Paasivirta S. Pedersen J. Pohjoismäki J. Salmela P. Vilkamaa H. Väre M. von Tschirnhaus T. Roslin 《Molecular ecology resources》2016,16(3):809-822
DNA sequences offer powerful tools for describing the members and interactions of natural communities. In this study, we establish the to‐date most comprehensive library of DNA barcodes for a terrestrial site, including all known macroscopic animals and vascular plants of an intensively studied area of the High Arctic, the Zackenberg Valley in Northeast Greenland. To demonstrate its utility, we apply the library to identify nearly 20 000 arthropod individuals from two Malaise traps, each operated for two summers. Drawing on this material, we estimate the coverage of previous morphology‐based species inventories, derive a snapshot of faunal turnover in space and time and describe the abundance and phenology of species in the rapidly changing arctic environment. Overall, 403 terrestrial animal and 160 vascular plant species were recorded by morphology‐based techniques. DNA barcodes (CO1) offered high resolution in discriminating among the local animal taxa, with 92% of morphologically distinguishable taxa assigned to unique Barcode Index Numbers (BINs) and 93% to monophyletic clusters. For vascular plants, resolution was lower, with 54% of species forming monophyletic clusters based on barcode regions rbcLa and ITS2. Malaise catches revealed 122 BINs not detected by previous sampling and DNA barcoding. The insect community was dominated by a few highly abundant taxa. Even closely related taxa differed in phenology, emphasizing the need for species‐level resolution when describing ongoing shifts in arctic communities and ecosystems. The DNA barcode library now established for Zackenberg offers new scope for such explorations, and for the detailed dissection of interspecific interactions throughout the community. 相似文献
73.
Burton A. Weiss 《Zoo biology》1990,9(6):421-429
A colony of the leaf-cutting Attine (Atta cephalotes isthmicola) ants was cultured and observed in the laboratory. During the 114 month life of the colony, a maximum garden volume of 54 L. was attained. The colony used a total of 139,902 g of substrate at a maximum rate of 2,660 g per month and occupied one hundred forty-four 1.25 L. chambers. Observations on the colony ranged from behavior of the castes to biochemistry and the absence of cholesterol. The dramatic display quality of Attine colonies for zoological exhibit is discussed. 相似文献
74.
LUKE HAYDEN GEORGE PARKES WALLACE ARTHUR 《Biological journal of the Linnean Society. Linnean Society of London》2012,107(1):166-174
There is a negative relationship between trunk segment number and latitude among geophilomorph centipedes in general. A similar relationship is known to exist within the most intensively‐studied geophilomorph species, Strigamia maritima, and also within several other species from this group. Previously, it was considered that this relationship did not involve body length; instead, individuals of S. maritima with more segments were considered to be more finely subdivided (not longer) than those with fewer segments. This incorrect interpretation arose from the difficulty of reliably separating post‐embryonic stages and thus of making a simple and direct comparison. In the present study, we build on recent work that facilitates such comparisons; and we show conclusively that individuals with more segments are longer. Our finding means that it is now possible to connect the work on S. maritima in particular, and on geophilomorph centipedes in general, with the debate about Bergmann's ‘rule’: the proposal that body size increases with increasing latitude. There is a clear ‘converse‐Bergmann’ pattern, as has been found in several other taxa. We propose an adaptive hypothesis that may explain why geophilomorphs show this pattern. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??. 相似文献
75.
为了解广西生态茶园与普通茶园节肢动物群落结构特点及其稳定性,本文采用Shannon-Wiener多样性指数(H′)、群落物种优势度指数(D)、丰富度指数(J)、物种均匀度指数(E)等分析了茶园节肢动物群落的多样性结构,应用群落相似度指数对生态茶园和普通茶园节肢动物的群落相似性进行了分析,用灰色关联度方法综合分析多样性指数与优势度、均匀度等6个特征参数间关系的密切程度。结果表明,在广西茶园节肢动物共34种,其中害虫(螨)17种,优势种群是:小贯小绿叶蝉Empoasca onukii Matsuda、茶蓟马Scirtothrips dorsalis Hood、蚜虫、白粉虱Trialeurodes vaporariorum Westwood;天敌8种,优势种群是:棕管巢蛛Clubiona japonicola Boeset Str.、八斑球腹蛛Theridion octomaculatum Boes. et Str.、异色瓢虫Harmonia axyridis(Pallas);中性昆虫9种,优势种群是:蚊虫、蚁类。多样性指数、群落均匀度指数与物种优势度在生态茶园比普通茶园高。生态茶园的群落稳定性比普通茶园的强。不同茶园间的群落相似性指数q在0.444~0.9355之间,群落间相似性关系在中等不相似与极度相似之间。与多样性指数密切相关的前3位群落特征参数依次是群落物种优势度、益害物种的个体数比、丰富度,其中关系最密切的特征参数是群落物种优势度。研究结果为茶园害虫的综合防控提供了理论依据。 相似文献
76.
Niche and dispersal ability are key traits for explaining the geographical structuring of species into discrete populations, and its evolutionary significance. Beyond their individual effects, the interplay between species niche and its geographic limits, together with the evolutionary lability of dispersal ability, can underpin trait diversification and speciation when exposed to gradients of selection. In this issue of Molecular Ecology, two complementary papers demonstrate how evolutionary lability for dispersal ability linked to niche shift can drive such a model in a context that includes selection. Both papers investigate the evolution of dispersal limitation in arthropods across altitudinal gradients, but using taxa with contrasting ecologies. McCulloch et al. (2019) investigate the evolution of wing loss at higher altitudes in stoneflies, a taxon inhabiting freshwater systems. Suzuki et al. (2019) report a similar phenomenon, but involving wing reduction at higher altitudes in scorpionflies, a taxon associated with moist terrestrial habitats. Here, we compare and contrast the results of both studies to explore their broader implications for understanding diversification and speciation within arthropods. 相似文献
77.
David A. Legg Mark D. Sutton Gregory D. Edgecombe Jean-Bernard Caron 《Proceedings. Biological sciences / The Royal Society》2012,279(1748):4699-4704
Extant arthropods are diverse and ubiquitous, forming a major constituent of most modern ecosystems. Evidence from early Palaeozoic Konservat Lagerstätten indicates that this has been the case since the Cambrian. Despite this, the details of arthropod origins remain obscure, although most hypotheses regard the first arthropods as benthic predators or scavengers such as the fuxianhuiids or megacheirans (‘great-appendage’ arthropods). Here, we describe a new arthropod from the Tulip Beds locality of the Burgess Shale Formation (Cambrian, series 3, stage 5) that possesses a weakly sclerotized thorax with filamentous appendages, encased in a bivalved carapace, and a strongly sclerotized, elongate abdomen and telson. A cladistic analysis resolved this taxon as the basal-most member of a paraphyletic grade of nekto-benthic forms with bivalved carapaces. This grade occurs at the base of Arthropoda (panarthropods with arthropodized trunk limbs) and suggests that arthrodization (sclerotization and jointing of the exoskeleton) evolved to facilitate swimming. Predatory and fully benthic habits evolved later in the euarthropod stem-lineage and are plesiomorphically retained in pycnogonids (sea spiders) and euchelicerates (horseshoe crabs and arachnids). 相似文献
78.
Wolbachia are bacterial endosymbionts that manipulate the reproduction of their arthropod hosts. Although theory suggests that infections are frequently lost within host species due to the evolution of resistance, Wolbachia infect a huge number of species worldwide. This apparent paradox suggests that horizontal transmission between host species has been a key factor in shaping the global Wolbachia pandemic. Because Wolbachia infections are thus acquired and lost like any other infection, we use a standard epidemiological model to analyse Wolbachia horizontal transmission dynamics over evolutionary time. Conceptually modifying the model, we apply it not to transmission between individuals but between species. Because, on evolutionary timescales, infections spread frequently between closely related species and occasionally over large phylogenetic distances, we represent the set of host species as a small‐world network that satisfies both requirements. Our model reproduces the effect of basic epidemiological parameters, which demonstrates the validity of our approach. We find that the ratio between transmission rate and recovery rate is crucial for determining the proportion of infected species (incidence) and that, in a given host network, the incidence may still be increasing over evolutionary time. Our results also point to the importance of occasional transmission over long phylogenetic distances for the observed high incidence levels of Wolbachia. In conclusion, we are able to explain why Wolbachia are so abundant among arthropods, although selection for resistance within hosts often leads to infection loss. Furthermore, our unorthodox approach of using epidemiology in evolutionary time can be applied to all symbionts that use horizontal transmission to infect new hosts. 相似文献
79.
Kevin D. Floate George K. Kyei-Poku Paul C. Coghlin 《Biocontrol Science and Technology》2006,16(8):767-788
Wolbachia bacteria are an unsuspected, but potentially important, component of many biocontrol programs. To heighten awareness of these bacteria, we review current knowledge of Wolbachia and their possible application in biocontrol research. Wolbachia promote their spread by altering the reproductive success of their arthropod hosts. This ability frequently is identified as having potential either to reduce populations of pest species, or to increase populations of beneficial species. However, only 19 and 1% of peer-reviewed research articles (n=844) on Wolbachia appear in arthropod- and biocontrol-specific journals, respectively. Although Wolbachia will not have application for all programs, their prevalence cannot be denied. We screened for Wolbachia in populations of arthropods of current interest to biocontrol programs in Canada. Infections were detected in 47% of 177 populations, representing 46% of the 105 species tested. Greater awareness, in combination with the rapidly expanding knowledge base of Wolbachia and similar endosymbionts, offers new directions for research in biocontrol programs. We recommend that all arthropod species in biocontrol programs be screened for these bacteria. 相似文献
80.
Bangert RK Turek RJ Rehill B Wimp GM Schweitzer JA Allan GJ Bailey JK Martinsen GD Keim P Lindroth RL Whitham TG 《Molecular ecology》2006,15(5):1379-1391
We define a genetic similarity rule that predicts how genetic variation in a dominant plant affects the structure of an arthropod community. This rule applies to hybridizing cottonwood species where plant genetic variation determines plant-animal interactions and structures a dependent community of leaf-modifying arthropods. Because the associated arthropod community is expected to respond to important plant traits, we also tested whether plant chemical composition is one potential intermediate link between plant genes and arthropod community composition. Two lines of evidence support our genetic similarity rule. First, in a common garden experiment we found that trees with similar genetic compositions had similar chemical compositions and similar arthropod compositions. Second, in a wild population, we found a similar relationship between genetic similarity in cottonwoods and the dependent arthropod community. Field data demonstrate that the relationship between genes and arthropods was also significant when the hybrids were analysed alone, i.e. the pattern is not dependent upon the inclusion of both parental species. Because plant-animal interactions and natural hybridization are common to diverse plant taxa, we suggest that a genetic similarity rule is potentially applicable, and may be extended, to other systems and ecological processes. For example, plants with similar genetic compositions may exhibit similar litter decomposition rates. A corollary to this genetic similarity rule predicts that in systems with low plant genetic variability, the environment will be a stronger factor structuring the dependent community. Our findings argue that the genetic composition of a dominant plant can structure higher order ecological processes, thus placing community and ecosystem ecology within a genetic and evolutionary framework. A genetic similarity rule also has important conservation implications because the loss of genetic diversity in one species, especially dominant or keystone species that define many communities, may cascade to negatively affect the rest of the dependent community. 相似文献