Fur seals at Macquarie Island: post-sealing colonisation, trends in abundance and hybridisation of three species

Goldsworthy, Simon; McKenzie, Jane; Page, Brad; Lancaster, Melanie L.; Shaughnessy, Peter D.; Wynen, Louise P.; Robinson, Susan; Peters, Kristian J.; Baylis, Alastair M. M.; McIntosh, Rebecca R.

doi:10.1007/s00300-009-0645-y

Cited by 24 publications

(25 citation statements)

References 30 publications

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“…Differences in the timing of recolonisation by both sexes of A. gazella and A. tropicalis have most probably contributed to the high levels of hybridisation at Macquarie Island [19]. Subsequent establishment of breeding populations of both species has resulted in an overall decline in hybridisation, and neutral genetic markers indicate that both pure lineages are maintained in the population [18,20].…”

Section: Introductionmentioning

confidence: 99%

Molecular evolutionary rates predict both extinction and speciation in temperate angiosperm lineages

Lancaster

2010

BMC Evol Biol

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BackgroundA positive relationship between diversification (i.e., speciation) and nucleotide substitution rates is commonly reported for angiosperm clades. However, the underlying cause of this relationship is often unknown because multiple intrinsic and extrinsic factors can affect the relationship, and these have confounded previous attempts infer causation. Determining which factor drives this oft-reported correlation can lend insight into the macroevolutionary process.ResultsUsing a new database of 13 time-calibrated angiosperm phylogenies based on internal transcribed spacer (ITS) sequences, and controlling for extrinsic variables of life history and habitat, I evaluated several potential intrinsic causes of this correlation. Speciation rates (λ) and relative extinction rates (ε) were positively correlated with mean substitution rates, but were uncorrelated with substitution rate heterogeneity. It is unlikely that the positive diversification-substitution correlation is due to accelerated molecular evolution during speciation (e.g., via enhanced selection or drift), because punctuated increases in ITS rate (i.e., greater mean and variation in ITS rate for rapidly speciating clades) were not observed. Instead, fast molecular evolution likely increases speciation rate (via increased mutational variation as a substrate for selection and reproductive isolation) but also increases extinction (via mutational genetic load).ConclusionsIn general, these results predict that clades with higher background substitution rates may undergo successful diversification under new conditions while clades with lower substitution rates may experience decreased extinction during environmental stasis.

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Section: Introductionmentioning

confidence: 99%

Molecular evolutionary rates predict both extinction and speciation in temperate angiosperm lineages

Lancaster

2010

BMC Evol Biol

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“…Following the cessation of seal harvesting in the early 1900s, successful protection measures have enabled fur seal colonies to repopulate, resulting in the recovery of fur seal numbers at many rookeries across the Southern Ocean (Wilkinson and Bester, 1990;Goldsworthy et al, 2009;Waluda et al, 2010). For example, on Marion Island (46° 54' S, 37° 45' E) both Antarctic (Arctocephalus gazella) and sub-Antarctic (A. tropicalis) fur seal numbers have increased steadily between the mid-1990s and early twenty first century at mean rates of approximately 14.8% and 5.3% per annum respectively (Hofmeyr et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Fur seal populations facilitate establishment of exotic vascular plants

Haussmann

Rudolph

Kalwij

et al. 2013

Biological Conservation

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The cessation of seal harvesting has prompted a recovery of previously decimated fur seal (Arctocephalus gazella and A. tropicalis) populations across the Southern Ocean region.Although the associated increase in seal-related soil disturbance is known to impact indigenous vegetation, the effect of increasing fur seal numbers on exotic plant species is not yet clear. Here, we compare plant species composition and cover between 26 sites with 2 high fur seal impact paired with nearby control sites on sub-Antarctic Marion Island. Sealaffected sites had a significantly higher number and cover of exotic plants, specifically of the widespread sub-Antarctic invaders, Poa annua and Sagina procumbens, than control sites. Furthermore, some of the native species, most notably the disturbance-sensitive species, Blechnum penna-marina, were significantly less abundant in seal-affected sites compared to controls. We propose that this is a result of both physical trampling, which opens up niches for exotics by damaging natives, and nutrient enrichment of the soils, giving exotic species a competitive advantage over natives. While other studies have noticed associations between exotic plant species and indigenous animal disturbance, this is, to the best of our knowledge, the first study to empirically show that the successful recovery of fur seal populations can have undesirable side-effects such as the enhanced persistence of exotic plant species. We recommend that alien plant management plans specifically include areas of increased animal disturbance into their programmes.

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“…Hybrids among wild pinnipeds have been reported for Antarctic and subantarctic fur seals (Arctocephalus tropicalis) (Goldsworthy et al 1999), and harp and hooded seals (Cystophora cristata) (Kovacs et al 1997). Among the fur seals, hybridization rates were so high that they represented a risk to successful reestablishment of populations, but the frequency of crossing appears to be dropping as the numbers of animals recover, with site fidelity and somewhat different habitat preferences favoring breeding true, inducing declines in hybridization rates (Goldsworthy et al 2009;Lancaster et al 2010). Among cetaceans, fin (Balaenoptera physalus) and blue whale (B. musculus) crosses have been documented Spilliaert et al 1991;Berube and Aguilar, 1998), as well as hybrids between Dall's (Phocoenoides dallii) and harbor porpoises (Baird et al 1998;Willis et al 2004).…”

Section: Mitochondrial Dna (Mtdna) Analysismentioning

confidence: 96%

Population Structure and Dynamics

Berta

2015

Marine Mammals

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Fur seals at Macquarie Island: post-sealing colonisation, trends in abundance and hybridisation of three species

Cited by 24 publications

References 30 publications

Molecular evolutionary rates predict both extinction and speciation in temperate angiosperm lineages

Molecular evolutionary rates predict both extinction and speciation in temperate angiosperm lineages

Fur seal populations facilitate establishment of exotic vascular plants

Population Structure and Dynamics

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