Anthropogenic Harvesting Pressure and Changes in Life History: Insights from a Rocky Intertidal Limpet

The importance of large breeding individuals for maintaining the health of marine fish and invertebrate populations has long been recognized. Unfortunately, decades of human harvesting that preferentially remove larger individuals have led to drastic reductions in body sizes of many of these species. Such size-selective harvesting is particularly worrisome for sequentially hermaphroditic species where the larger size classes are composed primarily of one sex. Whether these species can maintain stable sex ratios under sustained harvesting pressure depends on the level of plasticity of their life-history traits. Here, we show that populations of a marine limpet (Lottia gigantea) can adjust a fundamental aspect of their life history (the timing of sex change) when subjected to size-selective harvesting. As predicted by theoretical models, individuals from harvested populations change sex at smaller sizes and grow at slower rates compared to individuals from protected populations. In addition, the relative size at which the change from male to female occurs remains constant (?0.75; size at sex change/maximum size) across populations, regardless of harvesting pressure. Our results show that population-level demographic and life-history data, in conjunction with existing theory, can be sufficient to predict the responses of sequential hermaphrodites to harvesting pressure. Furthermore, they suggest such species can potentially adapt to size-selective harvesting

Historical and recent processes shaping the geographic range of a rocky intertidal gastropod: phylogeography, ecology, and habitat availability

Factors shaping the geographic range of a species can be identified when phylogeographic patterns are combined with data on contemporary and historical geographic distribution, range-wide abundance, habitat / food availability and through comparisons with co-distributed taxa. Here, we evaluate range dynamism and phylogeography of the rocky intertidal gastropod Mexacanthina lugubris lugubris across its geographic range - the Pacific coast of the Baja peninsula and southern California. We sequenced mitochondrial DNA (CO1) from ten populations and compliment these data with museum records, habitat availability and range-wide field surveys of the distribution and abundance of M. l. lugubris and its primary prey (the barnacle Chthamalus fissus). The geographic range of M. l. lugubris can be characterized by three different events in its history: an old sundering in the mid-peninsular region of Baja (~ 417,000 years ago) and more recent northern range expansion and southern range contraction. The mid-peninsular break is shared with many terrestrial and marine species, although M. l. lugubris represents the first mollusc to show it. This common break is often attributed to a hypothesized ancient seaway bisecting the peninsula, but for M. l. lugubris it may result from large habitat gaps in the southern clade. Northern clade populations, particularly near the historical northern limit (prior to the 1970’s) have high local abundances and reside in a region with plentiful food and habitat – which makes its northern range conducive to expansion. The observed southern range contraction may result from the opposite scenario, with little food or habitat nearby. Our study highlights the importance of taking an integrative approach to understanding the processes that shape the geographic range of a species via combining range-wide phylogeography data with temporal geographic distributions and spatial patterns of habitat / food availability

Intraspecific home range scaling: a case study from the owl limpet (Lottia gigantea)

Background: The owl limpet (Lottia gigantea) is an ectothermic invertebrate that inhabits the rocky intertidal zone where it territorially defends home ranges and grazes algae growing on the rocks. Among endothermic species, home range scales isometrically with body mass. Hypothesis: Home range area scales isometrically (scaling exponent ∼1.0) across individuals of the owl limpet, spanning more than an order of magnitude in body mass. Field sites: Southern and central California rocky intertidal sites (n = 5; ∼32.5–35.5 N). Methods: Measure home range area and body mass of individuals (n = 104). Determine the scaling exponent. Conclusions: Home range scaling across individuals of L. gigantea exhibits the same isometric relationship that is often found across endothermic species.Keywords: Size-selective harvesting, Ectothermic invertebrate, Allometry, Lottia gigantea, Home range scalin

Anthropogenic Harvesting Pressure and Changes in Life History: Insights from a Rocky Intertidal Limpet

The importance of large breeding individuals for maintaining the health of marine fish and invertebrate populations has long been recognized. Unfortunately, decades of human harvesting that preferentially remove larger individuals have led to drastic reductions in body sizes of many of these species. Such size-selective harvesting is particularly worrisome for sequentially hermaphroditic species where the larger size classes are composed primarily of one sex. Whether these species can maintain stable sex ratios under sustained harvesting pressure depends on the level of plasticity of their life-history traits. Here, we show that populations of a marine limpet (Lottia gigantea) can adjust a fundamental aspect of their life history (the timing of sex change) when subjected to size-selective harvesting. As predicted by theoretical models, individuals from harvested populations change sex at smaller sizes and grow at slower rates compared to individuals from protected populations. In addition, the relative size at which the change from male to female occurs remains constant (similar to 0.75; size at sex change/maximum size) across populations, regardless of harvesting pressure. Our results show that population-level demographic and life-history data, in conjunction with existing theory, can be sufficient to predict the responses of sequential hermaphrodites to harvesting pressure. Furthermore, they suggest such species can potentially adapt to size-selective harvesting.This is the publisher’s final pdf. The published article is copyrighted by University of Chicago and can be found at: http://www.press.uchicago.edu/journals.html.Keywords: Age, Sex change, Animals, Population structure, Growth, Body size, Fish, Southern California, Owl limpet, Lottia gigantea

Climate Change and Biosphere Response: Unlocking the Collections Vault

Natural history collections (NHCs) are an important source of the long-term data needed to understand how biota respond to ongoing anthropogenic climate change. These include taxon occurrence data for ecological modeling, as well as information that can be used to reconstruct mechanisms through which biota respond to changing climates. The full potential of NHCs for climate change research cannot be fully realized until high-quality data sets are conveniently accessible for research, but this requires that higher priority be placed on digitizing the holdings most useful for climate change research (e.g., whole-biota studies, time series, records of intensively sampled common taxa). Natural history collections must not neglect the proliferation of new information from efforts to understand how present-day ecosystems are responding to environmental change. These new directions require a strategic realignment for many NHC holders to complement their existing focus on taxonomy and systematics. To set these new priorities, we need strong partnerships between NHC holders and global change biologists

Macrobenthic mollusca of the Prince Gustav Channel, eastern Antarctic Peninsula: An area undergoing colonisation

In 2018 RRS James Clark Ross investigated the marine benthic biodiversity of the Prince Gustav Channel area which separates the eastern coast of the Antarctic Peninsula from James Ross Island. The southern end of this channel had been covered by the Prince Gustav Ice Shelf until its collapse in 1995. Benthic samples were collected by an epibenthic sledge at six stations (200–1,200 m depth) in the channel and adjacent Duse Bay. In total 20,307 live collected mollusc specimens belonging to 50 species and 4 classes (Solenogastres, Bivalvia, Gastropoda, and Scaphopoda) were identified. The area may be characterised by it’s low species richness (ranging from 7 to 39 species per station) but high abundances (specifically of the Scaphopods with 11,331 specimens). The functional traits of the community were dominated by motile development and mobility type. Assemblage analyses of the molluscan species abundances within the Prince Gustav Channel stations sit distinct, with no pattern by depth or location. However, when bivalve assemblages were analysed with reference to the wider Weddell Gyre region (15 stations from 300 to 2,000 m depth), the Prince Gustav Channel sits distinct from the other Weddell Gyre stations with a higher dissimilarity between the deeper or more geographically distant areas. The Prince Gustav Channel is undergoing colonisation following the recent ice shelf collapse. With many Antarctic ice shelves threatened under climate warming, this area, with future monitoring, may serve as a case study of benthic faunal succession

Campus Vol IX N 4

Howard Studio. Cover. Picture. 1. Anonymous. Untitled. Prose. 4. Cook, Mike. misty Mood . Prose. 5. McIntosh, Bruce. Misty Mood . Picture. 5. Pritchard, Joen. In the Good \u27Ole Summertime... . Prose. 6. Stout, Prentice. In the Good \u27Ole Summertime... . Picture. 6. Hodges, John. How to Choose a Roommate . Prose. 7. Tuttle, C. Untitled. Cartoon. 7. Fenberg, Geo. M. Students--- . Prose. 3. Wood and Knapp. Jokes From the Jazz Age as Flips From Flappers . Prose. 8. Greenlee, Midge. Nine to Five . Prose. 10. Anonymous. Mr. and Miss Campus-1954 . Picture. 11. Anonymous. Well Shut My Mouth! . Prose. 14. Tuttle, C. Untitled. Cartoon. 14.; Miller, John. The Drums of Ku . Poem. 14. Hodge, Beth. About Face . Picture. 15. Rasor, Tip. Sports Calendar . Prose. 16. Anonymous. Senior Will . Prose. 18. Kull, Shaw. Untitled. Cartoon. 23