Patterns Of Faunal Change Research Articles

Landscape-scale drivers of fish faunal homogenization and differentiation in the eastern United States

Establishment of nonnative fishes and extirpations of native fishes have homogenized freshwater fish faunas, yet our understanding of the drivers of this process remain limited. We addressed this knowledge gap by testing three hypotheses about introductions and homogenization of fish communities is the eastern United States: First, whether nonnative fish introductions have caused fish faunas to become homogenized or differentiated; second, whether patterns of faunal change are related to native species richness, propagule pressure, and anthropogenic disturbance; third, whether invasion patterns are attributable to either biotic resistance or preadaptation. We compared taxonomic similarity among watersheds in historical and contemporary time steps, and modeled contributions of different drivers to faunal change within watersheds. Average similarity among watersheds nearly doubled in contemporary times, pointing to substantial fish faunal homogenization. No watersheds lost species; patterns of homogenization are attributable entirely to nonnative species invasion. Community change and nonnative richness were positively associated with agriculture-urban land use, recreational fishing demand, and elevation. Native richness negatively affected community change and nonnative richness. Nonnative species originated from watersheds with higher richness than the ones they invaded, suggesting a role for biotic resistance. Understanding how mechanisms operate across spatial scales will help guide future conservation efforts.

Pronounced biotic and environmental change across the latest Danian warming event (LDE) at Shatsky Rise, Pacific Ocean (ODP Site 1210)

Abstract The early Paleogene is characterized by numerous hyperthermals, transient ( Nuttallides umbonifera dominated assemblage. Yet, ~ 200 kyr before the LDE, benthic foraminiferal assemblages, with increased relative abundance of endobenthic morphotypes and benthic foraminiferal accumulation rates indicate a slightly enhanced food flux. A temperature increase ~ 40 kyr before the first carbon isotope excursion (CIE) of the LDE (= LDE1) is associated with a rise in abundance of Tappanina selmensis , suggesting episodic input of fresh phytodetritus. At the start of LDE1, and through the second CIE (= LDE2), the seafloor returned to more oligotrophic conditions. Between 220 and 430 kyr after the onset of the LDE, a second phase of episodic fresh phytodetritus input is suggested by a renewed dominance of T. selmensis . Although the patterns of faunal change during hyperthermals relate to local conditions (circulation patterns), the magnitude of faunal change is probably more related to an absolute temperature threshold.

COMPARATIVE TAPHONOMY OF THE MAMMALIAN REMAINS FROM THE CABBAGE PATCH BEDS OF WESTERN MONTANA (RENOVA FORMATION, ARIKAREEAN): CONTRASTING DEPOSITIONAL ENVIRONMENTS AND SPECIMEN PRESERVATION

The study of faunal change through time in the fossil record requires a careful assessment of the potential biases introduced by the filtering of death assemblages by depositional environments and other agents of accumulation such as predators. The investigation of taphonomy of the mammalian remains from the Arikareean-aged Cabbage Patch beds of western Montana reported here used both sedimentological evidence and characteristics of the preservation of the fossil specimens to test two hypotheses regarding their preservation pattern: (1) the pattern of faunal change through the section is not a product of differences in the preservation of fossils and (2) the taphonomic characteristics of fossil specimens are linked to the environments in which they were preserved. The interpretation of the sedimentological data, combined with the analyses of the taphonomic filtering of mammalian fossils, suggests that the attritional accumulation of fossils in floodplain settings was the result of predator activity, attrition, and local reworking by fluvial processes. The fossils from these deposits experienced little transport. Moreover, despite complexities in the dataset, select specimen characteristics, including size, shape, and surface modifications, can be linked to the depositional environments determined from sedimentological data. The fossils recovered from a high energy deposit of the lower Cabbage Patch are significantly different from those found in low energy deposits. These low depositional energy fossil assemblages appear to be sufficiently taphonomically similar to be used in faunal analyses despite a change in postmortem filtering through the section.

Freshwater fish introductions in mediterranean‐climate regions: are there commonalities in the conservation problem?

AbstractAim To compare patterns and drivers of freshwater fish introductions across five climatically similar regions and evaluate similarities and differences in the non‐native species introduced.Location Five mediterranean‐climate regions: California (USA), central Chile, south‐western Australia, the Iberian peninsula (Spain and Portugal) and the south‐western Cape (South Africa).Methods Species presence–absence for native and non‐native fishes were collated across the regions, and patterns of faunal change were examined using univariate and multivariate statistical approaches. Taxonomic patterns in freshwater fish introductions were evaluated by comparing the number of species introduced by order to the numbers expected from binomial probabilities. Factors influencing multiple introductions of freshwater fish species in mediterranean regions were determined using generalized linear modelling.Results High levels of endemism (70–90%) were revealed for south‐western Cape, south‐western Australia and Chile. Despite their high rates of endemism, all regions currently have more non‐native species than endemic species. Taxonomic selection was found for five orders, although this was only significant for Salmoniformes across regions. The average increase in regional compositional similarity of fish faunas resulting from non‐native fish introductions was 8.0%. Important factors predicting multiple introductions of a species include previous introduction success and mean latitude of its distributionMain conclusions The mediterranean‐climate regions of the world, separated by vast distances, originally had a few fish species in common but are now more similar, owing to species introductions, illustrating the extent and importance of taxonomic homogenization. Introductions are largely driven by taxonomically biased human interests in recreational fisheries, aquaculture and ornamental pet species.

Spatial-temporal distribution of preimaginal blackflies in Neotropical streams

The current study investigates the spatial-temporal distribution of preimaginal blackflies in three ap rioriestablished, adjacent areas of Brazil and Venezuela. First we tested the hypothesis that the distribution of individual simuliid species, over two geographic scales, were predictable on the basis of several habitat parameters. Secondly, we determined if local species assemblages remain constant over two spatial axes, i.e., were species assemblages predictable within and between defined regions. Finally we compared the species assemblage between Venezuelan streams sampled in both the wet (October) and dry (February) seasons. As stream conditions changed across a north–south gradient, so did the occurrence of the most common species. This change in species composition from upland to lowland areas is consistent with the patterns of faunal change seen in North American simuliid assemblages. Discriminant Function Analysis showed a strong association between regional demarcations and stream site conditions. These results were paralleled by the strong correspondence between species assemblages and these regions. Thus each region presented both distinct stream environments and species assemblages. Monte Carlo analysis suggests that some if not all species are not only present in both the wet and dry season but that they are continuing to use the same stream sites. Three broad contingent rules for blackfly species assemblages in new world streams are put forward; (i) the ubiquitous nature of simuliids; (ii) species often distribute themselves along an axis of stream size and; (iii) there is a strong and consistent correspondence between regional characteristics of streams and the species assemblage.

応用古生物学 古生物学者による環境研究の事例 日本海における過去の温暖化に対する貝類の応答様式

Major changes occurred in the benthic molluscan fauna of the Sea of Japan continental shelf during the transition from Pleistocene glacial to interglacial stages, owing to rapid warming associated with the inflow of the warm Tsushima Current. Molluscan associations representing this transition occur in the lower Pleistocene Omma Formation in central Japan and suggest that there were two patterns of faunal change. The first was when warm-water species migrated into the Sea of Japan and lived along with cold-water species, accompanied by a northward shift in species ranges. The second pattern involved the migration of warm-water mollusks shortly after the local extinction of cold-water species. In the latter, it is possible that benthic molluscan communities with very low diversity and density extended a few km laterally and a few tens of meters vertically on the southern Sea of Japan inner-to outer-shelf. Such environment may have temporarily prevailed at least three times during early Pleistocene deglacial periods. These deglaciations corresponded to the three highest peaks of July solar insolation at 65°N during oxygen isotope stages from 50 to 28. This anomalously high seasonality forced by orbital insolation cycles is likely to have played an important role in establishing non-analogous benthic mollusk communities with very low density and diversity in the early Pleistocene Sea of Japan.

Molluscan response to early Pleistocene rapid warming in the Sea of Japan

Major changes occurred in the benthic molluscan fauna of the Sea of Japan continental shelf during the transition from Pleistocene glacial to interglacial stages, owing to rapid warming associated with the inflow of the warm Tsushima Current. Molluscan associations representing this transition occur in the lower Pleistocene Omma Formation in central Japan and suggest that there were two patterns of faunal change. The first was when warm-water species migrated into the Sea of Japan and lived along with cold-water species, accompanied by a northward shift in species ranges. The second pattern involved the migration of warm-water mollusks shortly after the local extinction of cold-water species. In the latter, it is possible that benthic molluscan communities with very low diversity and density existed temporarily and locally at inner shelf depths (<100 m) during the warming phase. Such a community has no modern analogue, but may have resulted from a marine climate with a higher seasonality than occurs today. These findings show that episodes of rapid warming have severe impacts on offshore benthic communities and molluscan species that include patterns not represented by modern faunal distributions.

Mammalian generic diversity and turnover in the late Paleocene and early Eocene of the Bighorn and Crazy Mountains Basins, Wyoming and Montana (USA)

Abstract Patterns of mammalian generic turnover, richness, and faunal composition were investigated for faunas from 17 biostratigraphic zones in middle Paleocene through early Eocene deposits of the Bighorn and Clarks Fork basins of northern Wyoming and the Crazy Mountains Basin of south-central Montana. Significance of turnover was evaluated (1) by comparison of observed turnover to expected turnover (calculated from the multiple regression of turnover on zone duration and generic richness), and (2) by comparison of observed turnover to a bootstrapped turnover distribution. Patterns of turnover and richness also were assessed in light of relative sampling quality of each faunal zone. The analysis identified four intervals of significant faunal change: the Torrejonian Tiffanian transition, the late Tiffanian, the earliest Wasatchian, and the middle-to-late Wasatchian. The first interval was characterized by a high number of last occurrences in the latest Torrejonian, resulting in a decrease in standing generic richness in the earliest Tiffanian, but no major changes in ordinal composition. During the next interval of significant turnover, the late Tiffanian, higher-than-expected first occurrences resulted in an increase in standing richness and a change in faunal composition, most probably reflecting the immigration of taxa from outside North America. The third, and most dramatic, interval of significant generic turnover took place in the earliest Wasatchian and was distinguished by a high number of first occurrences, but relatively few last occurrences. This led to a marked increase in generic richness, a pattern similar to that for the early Wasatchian of North America as a whole. The major change in faunal composition, as in the late Tiffanian, was largely composed of immigrants from other continents. The pattern of faunal change during the early Wasatchian of the Bighorn Basin, along with evidence for global warming at the Paleocene-Eocene boundary, supports previous interpretations associating this episode in mammalian evolution with the opening of high latitude intercontinental dispersal routes. During the fourth interval of interest, the middle to late Wasatchian, the Bighorn Basin fossil record shows a drop in generic richness. This differs from the overall North American pattern, and may be, in part, an artifact of still inadequate sampling for the latest part of the stratigraphic sequence in the Bighorn Basin.

Chironomidae from cow green reservoir and its environs in the first years of its existence (1970–1977)

Abstract The development of the chironomid fauna of Cow Green reservoir in marginal sublittoral and profundal areas is described for the first few years of the reservoir's life. A total of 71 chironomid taxa in 38 genera were identified from the reservoir and its immediate environs. The number of taxa taken directly from the reservoir was 44 of which only 15 were standing‐water species. Between 1970 and 1977 there was an increase in the proportion of standing‐water species from 30 to 62.5%. Orthocladiinae, particularly Psectrocladius and Orthocladius dominated marginal zones (< 1 m). Sublittoral areas (3–6 m) were characterised initially by Orthocladiinae and Tanytarsini but by the third year a more diverse community developed which included relatively high proportions of Chironomini and Tanypodinae. The clearest pattern of faunal change was observed in the profundal (15–18 m) where primary colonizers, consisting mainly of Orthocladiinae, gave way to an intermediate community dominated numerically by Tany...