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Butterfly dispersal and longevity in unlogged and selectively logged forest
... Hence we suggest that those studies in which this timespan was regarded as a mean life span [e.g. 85,86 ] should be treated cautiously. Instead, we recommend proper modeling of survival and estimation of life span distributions, such as we performed in our present study. ...
Adult survival and longevity in insects are key life-history traits, but their variation between sexes and individuals in natural populations is largely unexplored. Sexual divergence in senescence, the decline in survival with age is also poorly understood. Based on an intensive mark-recapture dataset of the butterfly Polyommatus daphnis, we aimed to assess whether adult survival is age-dependent, and to estimate life span distribution and abundance of males and females using Cormack-Jolly-Seber and Jolly-Seber models. Female survival slightly increased with date of emergence and slightly decreased with age, while male survival considerably declined with age. Mean life span of females (12.7 days) was ~50% higher than that of males (8.5 days), but two times higher if only the oldest 5% of each sex was considered (39 vs.19 days). Abundance of females (358 ± 14) and males (359 ± 11) was similar, but peak abundance of males preceded that of females by 11 days. Our results suggest that senescence is much more rapid in males than in females in this butterfly, which is in agreement with sexual selection theory. We also conclude that estimating life span distributions provides much more valuable information on the demography of natural populations than simply reporting the mean life span.
In many cases, the designation of Protected Areas (PAs) is not based on biological information, particularly in tropical regions where such information is generally lacking. Thus it is unclear whether tropical PAs are well-placed for conserving biodiversity currently, or under future climate change. We used reserve-design software (‘Zonation’) to investigate current and future conservation value of PAs of Thailand (N = 187 PAs, covering ∼20% of Thailand) in relation to forest-cover and butterfly diversity. Currently, PAs are about 2 °C cooler than non-PAs because PAs tend to occur at higher elevation (66% of land above 1000 m is protected compared with only 6% below 250 m). Temperature is predicted to increase in Thailand in future, but PAs are predicted to remain ∼2 °C cooler than non-PAs in future. We obtained modelled distribution data for 161 butterfly species (∼12% of national butterfly fauna), and used Zonation to rank areas (∼1 km2 grid resolution) based on species richness, complementarity, and forest cover. The conservation value of PAs was approximately twice that of non-PA areas, although many highly-ranked areas are not currently protected. The species richness of PAs was projected to decline by ∼30% in future, but the relative conservation rankings of individual PAs were projected to change very little. The preponderance of PAs in montane regions makes them well-placed to support forest species shifting from areas at lower elevation that become climatically unsuitable in future. By contrast, the conservation value of low-elevation PAs may decline in future if climate conditions become unsuitable for species.
Throughout the world, previously extensive areas of natural habitats have been degraded and fragmented, and improving habitat
connectivity may help the long-term persistence of species, and their ability to adapt to climate changes. We focused on Borneo,
where many remaining areas of tropical forest are highly fragmented, and we assessed the extent to which Protected Areas (PAs)
protect highly-connected forest sites. We analysed remotely-sensed land cover data (0.86km2 grid cell resolution) using ‘Zonation’ reserve design software, and we ranked grid cells (rank 0–1) according to forest extent
and connectivity. PAs currently cover 9% of Borneo, but <20% of highly-connected cells (i.e. cells with Zonation ranks ≥0.9)
lie within PAs. Approximately 65% of highly-connected cells were located above 400m elevation, although >60% of Borneo’s
total land area lies below 200m and only 15% of highly-connected cells occurred in these low elevation areas. These findings
were relatively insensitive to assumptions about species’ dispersal ability (within the range 1–20km; representing relatively
mobile animal species). The percentage of highly-connected grid cells within PAs could rise from <20 to >50% under proposed
new PAs (including the ‘Heart of Borneo’ project), although many other highly-connected sites will remain unprotected. On-going
land-use changes mean that existing PAs in lowland areas are likely to become increasingly isolated within inhospitable agricultural
landscapes, and improving connectivity through reforestation and rehabilitation of degraded forest may be required to maintain
the conservation value of these PAs in future.
KeywordsLandscape permeability–Reserve design–SE Asia–Landscape prioritization–Climate change adaptation
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