Nursing Females are More Prone to Heat Stress: Demography Matters When Managing Flying-Foxes for Climate Change

Determining the underlying mechanisms responsible for species-specific responses to climate change is important from a species management perspective. The grey-headed flying-fox, Pteropus poliocephalus, is listed as vulnerable but it also a significant pest species for orchardists and thereby presents an interesting management conundrum. Over the last century, the abundance of the grey-headed flying-fox, P. poliocephalus, in Australia has decreased due to a variety of threatening processes but has increased in abundance in urban areas. These flying-foxes are highly susceptible to extreme heat events which are predicted to increase in the future under climate change scenarios. Exceptionally hot days result in many deaths, the majority of whom are females with dependent young. This study examined the behavioural responses of roosting P. poliocephalus to temperature during the summer in their daytime roosts. Bats spent about 30% of their time resting at low temperatures, however, as temperature increased, fanning displaced resting as the predominant behaviour as bats attempted to cool themselves. Females with nursing young fanned significantly more often (P = 0.001) and at a higher rate with rising temperature (P \u3c 0.001) than males and females without young (average proportion of time fanning 27%, 19% and 16%, and 4.6, 2.8 and 2.5 for gradient respectively). As a consequence, nursing females also rested less with rising temperature than the other demographic groups (P \u3c 0.001). These behavioural indicators suggest that nursing mothers are more vulnerable to heat stress than any other demographic category studied. The data highlight a clear need to monitor the most vulnerable demographic units as part of any species management program

Non-Invasive Genetic Sampling of Faecal Material and Hair from the Grey-Headed Flying-Fox (Pteropus poliocephalus)

Remote-sampling DNA from animals offers obvious benefits for species that are difficult to sample directly and is less disruptive for species of conservation concern. Here we report the results of a pilot study investigating non-invasive DNA sampling of the grey-headed flying-fox (Pteropus poliocephalus), a threatened species that is restricted to the east coast of Australia. We successfully extracted DNA from fresh scats and hair, each of which was of sufficient quality for amplifying mitochondrial DNA markers and microsatellites. A single-locus multitube approach was used to investigate amplification success and genotyping reliability. Faecal samples yielded a higher proportion of successful amplifications and consensus genotype assignments than hair samples. We outline measures that may be utilised to minimise microsatellite genotyping error for future studies. These indirect approaches to obtaining genetic data show much promise given the difficult nature of directly sampling flying-foxes and related species

Microclimate Preferences of the Grey-Headed Flying Fox (Pteropus poliocephalus) in the Sydney Region

The population size of the grey-headed flying fox (Pteropus poliocephalus) has decreased dramatically as a result of a variety of threatening processes. This species spends a great proportion of time in roosting large social aggregations in urban areas, causing conflict between wildlife and humans. Little is known about why these bats choose to roost in some locations in preference to others. Roost selection by cave-dwelling bats can be greatly influenced by microclimatic variables; however, far less is known about microclimate selection in tree-roosting species despite the direct management implications. This study aimed to determine the microclimate characteristics of P. poliocephalus camps. Temperature and humidity data were collected via data-loggers located both in six camps and the bushland immediately adjacent to the camps in the greater Sydney region. We found significant differences between the microclimate within the camps and the surrounding bushland. In general, areas within the camps had a greater variance in temperature and humidity than the alternative locations. We hypothesise that camps may be specifically located in areas with high microclimate variance to accommodate a range of individual preferences that vary depending on demography

Microclimate preferences in the grey-headed flying fox in the Sydney region

The population size of the grey-headed flying fox (Pteropus poliocephalus) has decreased dramatically as a result of a variety of threatening processes. This species spends a great proportion of time in roosting large social aggregations in urban areas, causing conflict between wildlife and humans. Little is known about why these bats choose to roost in some locations in preference to others. Roost selection by cave-dwelling bats can be greatly influenced by microclimatic variables; however, far less is known about microclimate selection in tree-roosting species despite the direct management implications. This study aimed to determine the microclimate characteristics of P. poliocephalus camps. Temperature and humidity data were collected via data-loggers located both in six camps and the bushland immediately adjacent to the camps in the greater Sydney region. We found significant differences between the microclimate within the camps and the surrounding bushland. In general, areas within the camps had a greater variance in temperature and humidity than the alternative locations. We hypothesise that camps may be specifically located in areas with high microclimate variance to accommodate a range of individual preferences that vary depending on demography.8 page(s

Acquired resistance to BRAF inhibition can confer cross-resistance to combined BRAF/MEK inhibition

Aberrant activation of the BRAF kinase occurs in ~60% of melanomas, and although BRAF inhibitors have shown significant early clinical success, acquired resistance occurs in most patients. Resistance to chronic BRAF inhibition often involves reactivation of mitogen-activated protein kinase (MAPK) signaling, and the combined targeting of BRAF and its downstream target MAPK/ERK kinase (MEK) may delay or overcome resistance. To investigate the efficacy of combination BRAF and MEK inhibition, we generated melanoma cell clones resistant to the BRAF inhibitor GSK2118436. These BRAF inhibitor-resistant sublines acquired resistance through several distinct mechanisms, including the acquisition of activating N-RAS mutations and increased accumulation of COT1. These alterations uniformly promoted MAPK reactivation and most conferred resistance to MEK inhibition and to the concurrent inhibition of BRAF and MEK. These data indicate that melanoma tumors are likely to develop heterogeneous mechanisms of resistance, many of which will confer resistance to multiple MAPK inhibitory therapies. Corrigendum exists for this article and can be found in the Journal of investigative dermatology, 133(10), p. 2493, doi:10.1038/jid.2013.12510 page(s

Differential activity of MEK and ERK inhibitors in BRAF inhibitor resistant melanoma

Acquired resistance to BRAF inhibitors often involves MAPK re-activation, yet the MEK inhibitor trametinib showed minimal clinical activity in melanoma patients that had progressed on BRAF-inhibitor therapy. Selective ERK inhibitors have been proposed as alternative salvage therapies. We show that ERK inhibition is more potent than MEK inhibition at suppressing MAPK activity and inhibiting the proliferation of multiple BRAF inhibitor resistant melanoma cell models. Nevertheless, melanoma cells often failed to undergo apoptosis in response to ERK inhibition, because the relief of ERK-dependent negative feedback activated RAS and PI3K signalling. Consequently, the combination of ERK and PI3K/mTOR inhibition was effective at promoting cell death in all resistant melanoma cell models, and was substantially more potent than the MEK/PI3K/mTOR inhibitor combination. Our data indicate that a broader targeting strategy concurrently inhibiting ERK, rather than MEK, and PI3K/mTOR may circumvent BRAF inhibitor resistance, and should be considered during the clinical development of ERK inhibitors.11 page(s

Antiproliferative effects of continued mitogen-activated protein kinase pathway inhibition following acquired resistance to BRAF and/or MEK inhibition in melanoma

Inhibitors of the mitogen-activated protein kinases (MAPK), BRAF, and MAP-ERK kinase (MEK) induce tumor regression in the majority of patients with BRAF-mutant metastatic melanoma. The clinical benefit of MAPK inhibitors is restricted by the development of acquired resistance with half of those who benefit having progressed by 6 to 7 months and long-term responders uncommon. There remains no agreed treatment strategy on disease progression in these patients. Without published evidence, fears of accelerated disease progression on inhibitor withdrawal have led to the continuation of drugs beyond formal disease progression. We now show that treatment with MAPK inhibitors beyond disease progression can provide significant clinical benefit, and the withdrawal of these inhibitors led to a marked increase in the rate of disease progression in two patients. We also show that MAPK inhibitors retain partial activity in acquired resistant melanoma by examining drug-resistant clones generated to dabrafenib, trametinib, or the combination of these drugs. All resistant sublines displayed a markedly slower rate of proliferation when exposed to MAPK inhibitors, and this coincided with a reduction in MAPK signaling, decrease in bromodeoxyuridine incorporation, and S-phase inhibition. This cytostatic effect was also associated with diminished levels of cyclin D1 and p-pRb. Two shortterm melanoma cultures generated from resistant tumor biopsies also responded to MAPK inhibition, with comparable inhibitory changes in proliferation and MAPK signaling. These data provide a rationale for the continuation of BRAF and MEK inhibitors after disease progression and support the development of clinical trials to examine this strategy