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- Raia, P., et al.
(författare)
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Progress to extinction: increased specialisation causes the demise of animal clades
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Animal clades tend to follow a predictable path of waxing and waning during their existence, regardless of their total species richness or geographic coverage. Clades begin small and undifferentiated, then expand to a peak in diversity and range, only to shift into a rarely broken decline towards extinction. While this trajectory is now well documented and broadly recognised, the reasons underlying it remain obscure. In particular, it is unknown why clade extinction is universal and occurs with such surprising regularity. Current explanations for paleontological extinctions call on the growing costs of biological interactions, geological accidents, evolutionary traps, and mass extinctions. While these are effective causes of extinction, they mainly apply to species, not clades. Although mass extinctions is the undeniable cause for the demise of a sizeable number of major taxa, we show here that clades escaping them go extinct because of the widespread tendency of evolution to produce increasingly specialised, sympatric, and geographically restricted species over time.
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- Hannan, Johanna L., et al.
(författare)
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Impaired contraction and decreased detrusor innervation in a female rat model of pelvic neuropraxia
- 2017
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Ingår i: International Urogynecology Journal. - : Springer Science and Business Media LLC. - 0937-3462 .- 1433-3023. ; 28:7, s. 1049-1056
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Tidskriftsartikel (refereegranskat)abstract
- Introduction and hypothesis: Bilateral pelvic nerve injury (BPNI) is a model of post-radical hysterectomy neuropraxia, a common sequela. This study assessed the time course of changes to detrusor autonomic innervation, smooth muscle (SM) content and cholinergic-mediated contraction post-BPNI. Methods: Female Sprague–Dawley rats underwent BPNI or sham surgery and were evaluated 3, 7, 14, and 30 days post-BPNI (n = 8/group). Electrical field-stimulated (EFS) and carbachol-induced contractions were measured. Gene expression was assessed by qPCR for muscarinic receptor types 2 (M2) and 3 (M3), collagen type 1α1 and 3α1, and SM actin. Western blots measured M2 and M3 protein expression. Bladder sections were stained with Masson’s trichrome for SM content and immunofluorescence staining for nerve terminals expressing vesicular acetylcholine transporter (VAChT), tyrosine hydroxylase (TH), and neuronal nitric oxide synthase (nNOS). Results: Bilateral pelvic nerve injury caused larger bladders with less SM content and increased collagen type 1α1 and 3α1 gene expression. At early time points, cholinergic-mediated contraction increased, whereas EFS-mediated contraction decreased and returned to baseline by 30 days. Protein and gene expression of M3 was decreased 3 and 7 days post-BPNI, whereas M2 was unchanged. TH nerve terminals surrounding the detrusor decreased in all BPNI groups, whereas VAChT and nNOS terminals decreased 14 and 30 days post-BPNI. Conclusions: Bilateral pelvic nerve injury increased bladder size, impaired contractility, and decreased SM and autonomic innervation. Therapeutic strategies preventing nerve injury-mediated decline in neuronal input and SM content may prevent the development of a neurogenic bladder and improve quality of life after invasive pelvic surgery.
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- Piras, P., et al.
(författare)
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Evolution of the sabertooth mandible: A deadly ecomorphological specialization
- 2018
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Ingår i: Palaeogeography Palaeoclimatology Palaeoecology. - : Elsevier BV. - 0031-0182. ; 496, s. 166-174
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Tidskriftsartikel (refereegranskat)abstract
- Saber-toothed cats were armed with formidable weapons. They evolved a number of highly derived morphological features, most notably a pair of extremely long upper canines, which makes them unique within the felid family. Although the sabertooth character evolved several times among carnivorous mammals, sabertooth clades mostly had disjunctive occurrences both in space and time, and no sabertooth is alive today. We studied the rates of phenotypic and taxonomic diversification in the mandible of sabertooths, as compared to the rates calculated for both extinct and extant conical toothed cats. We found that the mandible's shape and physical properties in sabertooth clades evolved at distinctly higher rates than the rest of the felid tree. In addition, sabertooths had similar speciation rate to conical toothed cats, but statistically higher extinction rate. The wealth of morphological specializations required to be a sabertooth, and their tendency to focus on large-sized species as prey, was likely responsible for such high extinction rate, and for the peculiar, disjunctive patterns of sabertooth Glade occurrence in the fossil record.
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