1,721,100 research outputs found
A new species of Lethrinops (Cichliformes: Cichlidae) from a Lake Malawi satellite lake, believed to be extinct in the wild
No full textTurner, George F., Crampton, Denise A., Genner, Martin J. (2023): A new species of Lethrinops (Cichliformes: Cichlidae) from a Lake Malawi satellite lake, believed to be extinct in the wild. Zootaxa 5318 (4): 515-530, DOI: 10.11646/zootaxa.5318.4.5, URL: http://dx.doi.org/10.11646/zootaxa.5318.4.
Foraging of rocky habitat cichlid fishes in Lake Malawi: coexistence through niche partitioning?
No full textThe haplochromine cichlid fish communities of the rocky habitats of Lake Malawi are highly diverse; however, many species live side by side with apparently very similar resource requirements. There is a long-standing debate concerning whether these species partition their resources on a finer scale than has been previously reported or if species that are truly ecologically indistinguishable can coexist. A field study of food resource use was conducted to determine whether coexisting species segregate their diet and foraging sites. Significant differences between species were found, yet considerable inter-specific resource use overlap was commonplace. The data indicate that these cichlid species coexist both with and without niche differentiation. We propose that alternatives to niche differentiation should be considered to explain how many species coexist in Lake Malawi cichlid communities
Lethrinops lethrinus
No full text<i>Lethrinops lethrinus</i> (Günther, 1893) <p> <b>Holotype:</b> <i>Lethrinops lethrinus</i> (Günther, 1893): BMNH 1893.11.15.15, 116.1 mm SL, coll. A. Whyte, Upper Shire River at Fort Johnston (Mangochi), March 1892,</p>Published as part of <i>Turner, George F., Crampton, Denise A. & Genner, Martin J., 2023, A new species of Lethrinops (Cichliformes: Cichlidae) from a Lake Malawi satellite lake, believed to be extinct in the wild, pp. 515-530 in Zootaxa 5318 (4)</i> on page 526, DOI: 10.11646/zootaxa.5318.4.5, <a href="http://zenodo.org/record/8181908">http://zenodo.org/record/8181908</a>
Contrasting demographic histories of European and North American sea lamprey (Petromyzon marinus) populations inferred from mitochondrial DNA sequence variation
No full textPopulations of anadromous sea lamprey (Petromyzon marinus) have been found to be largely genetically homogeneous across western Europe, and across the eastern seaboard of North America. However, comparatively little is known of the relationship between the European and North American populations. We quantified the extent of population structuring present over a transatlantic scale using mitochondrial DNA sequences. We found clear segregation of the populations on either side of the Atlantic, and considerable genetic homogeneity within Europe over a spatial scale of over 2000 km. The North American populations contained larger genetic diversity than those from Europe, and coalescent analyses showed a corresponding greater overall effective population size. Employing calibration points based on a dated phylogeny of the Petromyzontiformes, our analyses indicated that the North American population has been increasing in effective size since establishment ~500 000 years ago, while the total European population has only undergone population expansion only within the last 125 000 years. This evidence is consistent with a colonisation of Europe from an older North American population, and with the European population persisting through the last glaciation within regional refugia
Lake level fluctuations and divergence of cichlid fish ecomorphs in Lake Tanganyika
Full text linkLake Tanganyika has undergone substantial climate-driven lake level fluctuations that have repeatedly changed the distribution and extent of habitat for endemic fishes. Here we consider whether patterns of population genetic structure and phenotypic divergence within the cichlid fish Telmatochromis temporalis have been associated with changing lake levels. The species has a large-bodied rock-living ecomorph and a small-bodied shell-living ecomorph, and both are found in close proximity in littoral habitats. Using mtDNA sequences we found that geographically distant (>50km) populations within the southern lake region diverged approximately 130,000-230,000 years ago, suggesting regional genetic structure persisted through a low stand of over 400 metres ~106,000 years ago that ended with a rise to present levels ~100,000 years ago. We also found signatures of large population expansions since this rise across the study region, suggesting populations positively responded to new habitat as lake levels rose to present levels. Finally, we found geographically adjacent (< 10 km) ecomorphs exhibit both significant genetic differentiation and signatures of gene flow after the lake level rise. The results suggest local ecomorph divergence progressed with gene flow after the last major rise in lake level ~100,000 years ago, potentially facilitated by new ecological opportunities
Detection of environmental change in a marine ecosystem—evidence from the western English Channel
No full textTo separate human-induced changes from natural fluctuations in marine life requires long-term research. The western English Channel has been investigated from Plymouth for over 100 years. The abundance of marine life has been recorded and related to physical changes in the environment. By comparing different parts of the ecosystem we can demonstrate historic natural fluctuations, allowing prediction of effects of future global change. From the 1920s to the 1950s there was a period of warming of the sea, with increases in abundance of species of fish, plankton and intertidal organisms that are typically common in warmer waters to the south of Britain. After 1962 the sea cooled down and northern cold-water species became more abundant. Since the 1980s regional sea surface temperature has increased again and warm-water species are once more becoming abundant
Minimalist barcodes for sponges:a case study classifying African freshwater Spongillida
Full text linkAfrican sponges, particularly freshwater sponges, are understudied relative to demosponges in most other geographical regions. Freshwater sponges (Spongillida) likely share a common ancestor; however, their evolutionary history, particularly during their radiation into endemic and allegedly cosmopolitan groups, is unclear. Freshwater sponges of at least 58 species of 17 genera and four families are described from Central and Eastern Africa, but the diversity is underestimated due to limited distinguishable morphological features. The discovery of additional cryptic species is very likely with the use of molecular techniques such as DNA barcoding. The Royal Museum of Central Africa (MRAC, Tervuren, Belgium) hosts one of the largest collections of (Central) African freshwater sponge type material. Type specimens in theory constitute ideal targets for molecular taxonomy; however, the success is frequently hampered by DNA degradation and deamination, which are a consequence of suboptimal preservation techniques. Therefore, we genotyped African demosponge holotype material of the MRAC with specific short primers suitable for degenerated tissue and compare the results with the current, morphology-based classification. Our results demonstrate the utility of minimalistic barcodes for identification of sponges, potentially enabling efficient identification of individuals in taxonomic or metabarcoding studies, and highlight inconsistencies in the current freshwater sponge classification
Persistence of environmental DNA in marine systems
Full text linkAs environmental DNA (eDNA) becomes an increasingly valuable resource for marine ecosystem monitoring, understanding variation in its persistence across contrasting environments is critical. Here, we quantify the breakdown of macrobial eDNA over a spatio-temporal axis of locally extreme conditions, varying from ocean-influenced offshore to urban-inshore, and between winter and summer. We report that eDNA degrades 1.6 times faster in the inshore environment than the offshore environment, but contrary to expectation we find no difference over season. Analysis of environmental covariables show a spatial gradient of salinity and a temporal gradient of pH, with salinity—or the biotic correlates thereof—most important. Based on our estimated inshore eDNA half-life and naturally occurring eDNA concentrations, we estimate that eDNA may be detected for around 48 h, offering potential to collect ecological community data of high local fidelity. We conclude by placing these results in the context of previously published eDNA decay rates
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