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1.
    
Abstract:  Little is known about predation of Mesozoic and Cenozoic articulated brachiopods, but it is far from clear whether this is because they suffered very little predation pressure or because there have been few attempts to search for evidence of it. A study of 248 museum specimens of the large Pliocene terebratulid Apletosia maxima from the Coralline Crag (UK) has revealed that more than 16 per cent of them show evidence of having been attacked by predators. The styles of damage can be attributed to drilling muricid gastropods (most of which were successful) and failed crushing attacks probably by decapods. Brachiopods are usually thought to offer a poor tissue yield to potential predators, but in this instance it appears that A. maxima was attractive to predators even though they were living with a rich molluscan fauna. It is suggested that the mass of adductor and diductor muscles (likely to be spicule-free) of these particularly large brachiopods may have made them profitable. Further studies of post-Palaeozoic brachiopod faunas are required, particularly those from mixed shallow-water communities, before it can be established whether articulated brachiopods have or have not been driven into refugia by increasing predation pressure.  相似文献   

2.
    

Shell repair frequencies in eleven species of Recent gastropods from the northern Gulf of California vary with habitat, shell morphology and intensity of durophagous predation. Squat shells with large apertures tend to have high repair frequencies (0.25–0.50). Shell thickness at the aperture and shell size are not correlated with frequency of repair. Significant intraspecific variation in repair frequency exists between habitats. Samples from rocky habitats have statistically higher repair frequencies than samples of the same species from sandy habitats. However, habitat‐related variation between species is not apparent.

Trends in co‐evolution of gastropods and their durophagous predators are based on the indirect evidence of shell repair frequencies through time. Variation in repair frequency due to environmental and morphological factors may obscure predator‐related temporal trends in repair frequency.  相似文献   

3.
Shell abnormalities in scaphitid ammonites   总被引:1,自引:0,他引:1  
The kinds incidence of shell abnormalities were investigated in over 2000 adult Late Cretaceous scaphitid ammonites. Most are species of Hoploscaphites Discoscaphites from the Maastrichtian Fox Hills Formation; for comparison, four older species of Scaphites were also studied. Four kinds of abnormalities vary in their incidence among the Fox Hills taxa but display no general trends. (1) Morton's syndrome, shell asymmetry unrelated to external injury, occurs in 3 to 6% of the Fox Hills scaphites. (2) Suture wander. veering-off of the ventral lobe of the suture from the midline of the venter, occurs in most Fox Hills taxa with an incidence ranging from 1 to 11%. (3) Stretch pathology, an attenuation of the shell on the posterior part of the adult body chamber, is confined to Hoploscaphifes nicolleti. (4) Externally inflicted injury, indicated by repaired damage on mature shells, has an average incidence of 10% in Fox Hills scaphites except in the stratigraphically youngest H. nebrascensis H. cheyennewis which approach 25 40% respectively. Good correlation between percent injuries adult size ornamentation is obtained only in Discoscaphifes; all morphs of the co-occurring Hoploscaphites display nearly the same incidence of injuries regardless of their morphologic variation. The stratigraphically youngest H. nebrascensis becomes larger more nodose simultaneously sustains more injuries. However, its dimorph H. cheyennensis remains morphologically unchanged although its incidence of injuries quadruples. These injury data, in themselves, do not support the hypothesis that predators were contributing more heavily to the mortality of Maastrichtian ammonites precipitated their extinction.  相似文献   

4.
    
Olev Vinn 《Historical Biology》2018,30(8):1043-1049
Series two marks a revolution in Cambrian predation when new predators and new predation methods appeared, which led to general increase in predation intensities and in the diversity of prey groups. The number of bored taxa and taxa with the predation scars is similar in the Cambrian. Most of the borings are associated with brachiopods and most of the scars with trilobites. Brachiopods, arthropods, molluscs, cnidarians and echinoderms were the most common prey in the Cambrian. The Cambrian record of predation is dominated by damage inflicted on brachiopods and trilobites. The fossils with predation signs are known from a majority of paleocontinents and all the Cambrian series.  相似文献   

5.
    
1. Investigating how climatic niches change over evolutionary timescales is a necessary step to understanding the current distribution of lineages, yet few studies have addressed this issue using comprehensive datasets. In this study, the evolution of ant climatic niches is investigated at a global scale based on bioclimatic data associated with 163 481 ant occurrence records. The resulting dataset was subjected to principal component analysis, and the scores obtained were used to characterise the main axes of ant climatic niche evolution. 2. Principal component axis 1 (PC1) reflected variation in average temperature and seasonality – consistent with typical tropical/temperate gradients – whereas PC2 was associated with varying levels of aridity. Evolution along these two niche axes was markedly different: differences in the amount of explained variance between PC1 (65%) and PC2 (19%) suggest that climatic niche evolution was nearly three times more pronounced along a tropical–temperate climate axis. 3. There was statistically significant phylogenetic signal on PC1, with genera occupying more tropical conditions diversifying at a faster rate, yet neither of these results is significant on PC2. In addition, most of the ancient ant lineages are associated with conditions of low seasonality and high temperatures. 4. These results provide partial support for the tropical conservatism hypothesis as an explanation for geographical patterns of ant species richness.  相似文献   

6.
    
The shell repair scars of modern Nautilus pompilius in the Philippines presumably due to sub‐lethal predatory attacks were examined throughout ontogeny ranging from hatching to maturity, revealing the higher risk of fatality in earlier ontogenetic stages. The examinations throughout ontogeny demonstrate that: (1) sub‐lethal predatory attacks by other organisms have no preferred position through ontogeny; (2) the sizes of shell repair scars are similar throughout ontogeny and, therefore, the width and length of shell repair scars relative to shell diameter decrease from hatching towards maturity; and (3) the proportion of sub‐lethal predatory attacks within 10 mm increments of shell diameter are similar irrespective of shell diameter or decrease approaching maturity. The numbers of the irregular, radiating, black shell repair scars, indicating injury to the soft parts at shell breakage, decrease at a diameter >80 mm and none were found at <56 mm in shell diameter. Furthermore, the rarity of juvenile trapping data might be related to the higher fatality from predatory attacks in earlier ontogenetic stages, providing crucial information for the conservation of N. pompilius.  相似文献   

7.
8.
    
Physiological and behavioural constraints arising from ecological specialisation are proposed to limit gene flow and promote diversification in tropical lineages. In this study, we use phylogenetic analyses to test this idea in 739 Amazonian bird species. We show that patterns of species and subspecies richness are best predicted by a suite of avian specialisms common in tropical avifaunas but rare in the temperate zone. However, this only applied to niche traits associated with dispersal limitation rather than vagility. These findings are consistent with the view that diversity is promoted by more finely partitioned niches, although not simply by coevolutionary adaptation and niche packing as is often assumed. Instead, they suggest that diversification is driven by dispersal constraints, and that niches characterised by these constraints are biased towards tropical systems. We conclude that specialised tropical niches reduce the likelihood of dispersal across barriers, thereby increasing allopatric diversification and contributing to the latitudinal diversity gradient.  相似文献   

9.
    
Stable isotopes in mollusc shells, together with variable growth rates and other geochemical properties, can register different environmental clues, including seawater temperature, salinity and primary productivity. However, the strict biological control over the construction of biominerals exerted by many calcifying organisms can constrain the use of these organisms for paleoenvironmental reconstructions. Biologically controlled calcification is responsible for the so called vital effects that cause a departure from isotopic equilibrium during shell formation, resulting in lower shell oxygen and carbon compared to the equilibrium value. We investigated shell oxygen and carbon isotopic composition of the bivalve Chamelea gallina in six sites along with a latitudinal gradient on the Adriatic Sea (NE Mediterranean Sea). Seawater δ18O and δ13CDIC varied from North to South, reflecting variations in seawater temperature, salinity, and chlorophyll concentration among sites. Shell δ18O and δ13C differed among sites and exhibited a wide range of values along with the ~400 km latitudinal gradient, away from isotopic equilibrium for both isotopes. These results hampered the utilization of this bivalve as a proxy for environmental reconstructions, in spite of C. gallina showing promise as a warm temperature proxy. Rigorous calibration studies with a precise insight of environment and shell growth are crucial prior to considering this bivalve as a reliable paleoclimatic archive.  相似文献   

10.
    
Repaired shell injuries occuring in less than four per cent of examined specimens of the platyceratid gastropod Praenatica gregaria (Barrande, in Perner 1903) from the Lower Devonian (Pragian) of Bohemia probably result from non–lethal predatory attacks. The low frequency may reflect the resistance of the large, smooth, rapidly expanding shell to attack, but a high rate of fatal attacks could produce the same pattern. The habit of some platyceratid gastropods living on echinoderm calices may provide a refuge from benthic predators, but conclusive evidence for this mode of life in P. gregaria or the general assumption of platyceratid coprophagy is lacking.  相似文献   

11.
Living specimens of Terebratulina retusa from the Firth of Lorn, Scotland, were surgically damaged by drilling 2 mm diameter holes or narrow slits one cm long in the anterior portion of one valve, by bevelling the anterior margin of both valves, or by amputation of the anterior third of one valve. These injuries to the shell and mantle simulated the type of repaired shell damage seen in Paleozoic species, i.e., scalloped, divoted, cleft, and embayed valves. Less than ten percent of the 200 damaged specimens survived until the 25th week after surgery. Specimens of T. retusa showed the ability to repair drill holes, slits, and bevelled anterior shell regions, but not the most severe damage, i.e., amputations of the anterior third of one valve. Shell‐repair was initiated in the fourth week after surgery by the development of a membrane across the wound. The development of caeca in the new shell layer secreted to plug the drill holes became apparent by the eighth week. The punctate pattern was complete in the new, translucent shell material of bevelled and drilled specimens by the 25th week following surgery. Failure of any specimens to survive amputation of the anterior portion of a valve for more than seven weeks after surgery, and the absence of initiation of the repair process, suggests that terebratulids do not have the tolerance for, nor the ability to repair, the severe injuries (embayed valves) which were sustained and mended by extinct strophomenids.  相似文献   

12.
Shell fragmentation patterns that result from attacks by durophagous predators on hard‐shelled marine invertebrates are a rich source of indirect evidence that have proved useful in interpreting predation pressure in the fossil record and recent ecology. The behaviour and effectiveness of predators are known to be variable with respect to prey size. It is less well understood if variable predator–prey interactions are reflected in shell fragmentation patterns. Therefore, we conducted experimental trials to test the behavioural response of a living crab, Carcinus maenas, during successful predatory attacks on the blue mussel Mytilus edulis on two prey size categories. Further, we examined resultant shell fragments to determine whether specific attack behaviours by C. maenas could be successfully deduced from remaining mussel shells. In contrast to previous studies, we observed no significant differences in attack behaviour by the predators attributable to prey size. In most experimental predation events, crabs employed an ad hoc combination of five mechanisms of predation previously described for this species. We identified seven categories of shell breakage in predated mussels, but none of these were unambiguously correlated with specific attack behaviour. Combined attack behaviours may produce shell breakage patterns that have previously been assumed to be attributable to a single behaviour. While specific patterns of shell breakage are clearly attributable to durophagy, the results of this study provide important insights into the limitations of indirect evidence to interpret ecological interactions.  相似文献   

13.
    

Aim

Greenland is one of the places on Earth where the effects of climate change are most evident. The retreat of sea ice has made East Greenland more accessible for longer periods during the year. East Greenland fjords have been notoriously difficult to study due to their remoteness, dense sea ice conditions and lack of infrastructure. As a result, biological monitoring across latitudinal gradients is scarce in East Greenland and relies on sporadic research cruises and trawl data from commercial vessels. We here aim to investigate the transition in fish and marine mammal communities from South to Northeast Greenland using environmental DNA (eDNA).

Location

South to Northeast Greenland.

Methods

We investigated the transition in fish and marine mammal communities from South to Northeast Greenland using eDNA metabarcoding of seawater samples. We included both surface and mesopelagic samples, collected over approximately 2400 km waterway distance, by sampling from Cape Farewell to Ella Island in August 2021.

Results

We demonstrate a clear transition in biological communities from south to northeast, with detected fish and mammal species matching known distributions. Samples from the southern areas were dominated by capelin (Mallotus villosus) and redfish (Sebastes), whereas northeastern samples were dominated by polar cod (Boreogadus saida), sculpins (Myoxocephalus) and ringed seal (Pusa hispida). We provide newly generated 12S rRNA barcodes from 87 fish species, bringing the public DNA database closer to full taxonomic coverage for Greenlandic fish species for this locus.

Main Conclusions

Our results demonstrate that eDNA sampling can detect latitudinal shifts in marine biological communities of the Arctic region, which can supplement traditional fish surveys in understanding species distributions and community compositions of marine vertebrates. Importantly, sampling of eDNA can be a feasible approach for detecting northward range expansions in remote areas as climate change progresses.  相似文献   

14.
    
Abstract:  Phosphatised limestone-hosted and shale-hosted specimens of the obolellid Mummpikia nuda gen. et comb. nov. and two further unidentified obolellids from the Early Cambrian Mural Formation (Jasper National Park, Canadian Rocky Mountains) provide novel insights into the shell microstructure of obolellids and the nature of their pedicle. The shell was penetrated by abundant canals of a sub- μ m diameter and the anterior tip of the delthyrium forms a projection into the body cavity that is penetrated by a thin canal. It is argued that both shell microstructure and posterior margin are linguliformean characters and that obolellids hold a position basal in the rhynchonelliform stem-group.  相似文献   

15.
The Kohl Ranch locality in the Naco Formation of central Arizona has yielded an abundant and diverse fauna including eight genera of brachiopods and four of sharks including Cochliodus. The most abundant brachiopod, Composita subtilita , was analyzed for predation damage and of 935 specimens 503 (53.7%) were found to show the type of unrepaired crushing previously attributed to shark predation. Reconstruction of the jaw of Cochliodus , however, suggests that it may have been a selective feeder similar to the modern Heterodontus and unlikely therefore to have left so many damaged but uningested specimens. Evidence from specimens collected in situ suggests that the damage mostly occurred post-mortem due to the compaction of the sediments and was not due to the sharks who would have comminuted any prey items taken.  相似文献   

16.
One hypothesis for the latitudinal gradient in species richness observed in most animal taxa is that the richness of a region is determined by its geographic area. However, the relationship between geographic area and species richness across regions is generally weak. It has been suggested that this is because species from the tropics spill out of this region of high richness, artificially inflating the richness of other regions. This generates the interesting prediction that the area and richness of extra-tropical regions should be more strongly correlated if tropical species are excluded. We test this prediction using the avifauna of the New World. We find that there is indeed a relationship between the land area and species richness of a region once tropical species are excluded. This relationship is independent of the latitude and productivity of regions. Both latitude and productivity can explain variance in richness unexplained by land area. There is no relationship between land area and species richness if tropical species are not excluded from the analysis, suggesting that tropical species do indeed mask the relationship between richness and area. We conclude that our results generally support the geographic area hypothesis, although tests of its other predictions and on other land masses are required.  相似文献   

17.
18.
    
  1. While the diversity of most taxa increases from temperate to tropical regions, the parasitoid wasp family Ichneumonidae has often been cited as an example of an anomalous diversity pattern with their highest diversity at mid‐latitudes. A rich body of literature has attempted to explain this pattern and provide hypothesised mechanisms, and recent studies have suggested that the pattern may result from biases in the data.
  2. Previous studies of patterns in ichneumonid diversity have mined catalogue data or have compared collections from tropical and temperate areas across a limited range of latitudes. Few studies are available that include species richness for all subfamilies, and none have been from regions above 60°N.
  3. To increase the number of datasets available to address these patterns, we first tested the assumption that subfamily abundance can be a strong predictor of species richness. We then compared abundances of ichneumonid subfamilies in field collections from a wide range of latitudes (25°S–81°N), and used generalised additive models to evaluate characteristics of the subfamilies as predictors of the observed patterns.
  4. We demonstrate a wide variety of latitudinal patterns, reflecting the ecological variation between subfamilies. In addition, our models show that host taxon and subfamily identities are better predictors of the shape of the relationship between subfamily abundance and latitude than other characteristics that have been previously hypothesised to be important, including parasitoid life history strategy and body size.
  相似文献   

19.
    
The fossil record holds a wealth of ecological data, including data on biotic interactions. For example, holes in the skeletons of invertebrates produced by drilling activities of their enemies are widely used for exploring the intensity of such interactions through time because they are common and easily distinguished from non-biotic holes or holes produced by other types of interactions. Such drill holes have been described in numerous studies of Palaeozoic brachiopods but rarely in those focusing on brachiopods of the post-Palaeozoic, a striking pattern given that in the late Mesozoic and Cenozoic drilling gastropods diversified and frequencies of drilled molluscs increased dramatically. During the past several years, however, drilled brachiopods were reported in several studies of the Mesozoic and Cenozoic, suggesting that this phenomenon may be more common than has been previously assumed. Here we report on drilled brachiopods from a Pliocene locality in Algeria where 90 of 261 (34.5%) specimens of Megerlia truncata show evidence of predatory drilling. These data confirm that Cenozoic drilling frequencies of brachiopods may be locally high and, when taken together with other published data, that drilling frequencies are highly heterogeneous in space and time.  相似文献   

20.
    
John S. Peel 《Palaeontology》2015,58(2):229-237
Regeneration of the calcareous rigiclaudent operculum following severe, non‐lethal, predatory attacks is described in two specimens of the characteristic Silurian gastropod Oriostoma from the English Midlands. This is the first record of the regeneration of opercula in Palaeozoic gastropods and of opercula conjoined with shells that have been repaired after significant, failed, durophagous attacks. In one specimen, a series of repaired injuries culminates in a repaired aperture closed by the operculum. In the second specimen, new shell growth has failed to recover the full extent of the original broken whorl, and the new aperture and operculum, though well developed, are smaller than the originals. Both opercula are unusually thin centrally when compared to other, strongly domed, Oriostoma opercula.  相似文献   

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