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1.
Until recently, studies of divergence and gene flow among closely‐related taxa were generally limited to pairs of sister taxa. However, organisms frequently exchange genes with other non‐sister taxa. The “northern oriole” group within genus Icterus exemplifies this problem. This group involves the extensively studied hybrid zone between Baltimore oriole (Icterus galbula) and Bullock's oriole (I. bullockii), an alleged hybrid zone between I. bullockii and black‐backed oriole (I. abeillei), and likely mtDNA introgression between I. galbula and I. abeillei. Here, we examine the divergence population genetics of the entire northern oriole group using a multipopulation Isolation‐with‐Migration (IM) model. In accordance with Haldane's rule, nuclear loci introgress extensively beyond the I. galbula–I. bullockii hybrid zone, while mtDNA does not. We found no evidence of introgression between I. bullockii and I. abeillei or between I. galbula and I. abeillei when all three species were analyzed together in a three‐population model. However, traditional pairwise analysis suggested some nuclear introgression from I. abeillei into I. galbula, probably reflecting genetic contributions from I. bullockii unaccounted for in a two‐population model. Thus, only by including all members of this group in the analysis was it possible to rigorously estimate the level of gene flow among these three closely related species. 相似文献
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J. David Wiens Robert G. Anthony Eric D. Forsman 《The Journal of wildlife management》2011,75(3):531-538
The range expansion by barred owls (Strix varia) into western North America has raised considerable concern regarding their potential effects on declining northern spotted owl (Strix occidentalis caurina) populations, yet most information on the occurrence of barred owls in the region is limited to incidental detections during surveys for spotted owls. To address this shortcoming we investigated response behavior, detection probabilities, and landscape occupancy patterns of barred owls in western Oregon, USA, during conspecific versus spotted owl call-broadcast surveys. Subtle differences in barred owl response behavior to conspecific versus spotted owl vocalizations combined with minor procedural differences between species-specific survey protocols led to a sizeable difference in estimated detection probabilities during conspecific (0.66, 95% CI = 0.61–0.71) versus spotted owl (0.48, 95% CI = 0.39–0.56) surveys. We identified 61 territorial pairs of barred owls during repeated surveys of a multi-ownership study area with the probability of occupancy being highest in the structurally diverse mixture of mature and old forests that occurred almost entirely on public lands. Our findings suggest that research and management strategies to address potential competitive interactions between spotted owls and barred owls will require carefully designed, species-specific survey methods that account for erratic response behaviors and imperfect detection of both species. Our sampling methods can be used by forest managers to determine the occurrence and distribution of barred owls with high confidence. © 2011 The Wildlife Society. 相似文献
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A male northern elephant seal (Mirounga angustirostris) that was conceived in captivity was stillborn February 14, 1981, at Mystic Marinelife Aquarium in Mystic, Connecticut. Either of two males in the exhibit could have sired the pup. Both were only 3 yr at the time of conception. 相似文献
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Gunnar ?hlund Per Hedstr?m Sven Norman Catherine L. Hein G?ran Englund 《Proceedings. Biological sciences / The Royal Society》2015,282(1799)
The temperature dependence of predation rates is a key issue for understanding and predicting the responses of ecosystems to climate change. Using a simple mechanistic model, we demonstrate that differences in the relative performances of predator and prey can cause strong threshold effects in the temperature dependence of attack rates. Empirical data on the attack rate of northern pike (Esox lucius) feeding on brown trout (Salmo trutta) confirm this result. Attack rates fell sharply below a threshold temperature of +11°C, which corresponded to a shift in relative performance of pike and brown trout with respect to maximum attack and escape swimming speeds. The average attack speed of pike was an order of magnitude lower than the escape speed of brown trout at 5°C, but approximately equal at temperatures above 11°C. Thresholds in the temperature dependence of ecological rates can create tipping points in the responses of ecosystems to increasing temperatures. Thus, identifying thresholds is crucial when predicting future effects of climate warming. 相似文献
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退耕还林还草工程对陕北地区生态系统服务价值时空演变的影响 总被引:5,自引:0,他引:5
基于陕北地区1990、2000、2015年土地利用数据,运用单位面积生态系统价值当量因子法、格网法、探索性空间数据法(ESDA),分析了退耕还林还草工程实施前后生态系统服务价值(ESV)的空间分布和演化规律,探讨了退耕还林还草工程对ESV的影响。结果表明:(1)陕北地区退耕还林还草工程实施效果显著,工程实施后共有297066.15 hm2耕地转化为林地和草地,林草覆盖率由57.33%增长至60.50%。(2)退耕还林还草工程使得陕北地区ESV得到了显著提升。25年间陕北地区ESV共增加了32.82亿元,ESV在工程实施后比工程实施前多增加了5.93亿元,增长主要源于退耕引起林地和草地面积的增加。(3)ESV空间分布上呈显著的“南高北低”分布格局,并表现出正向的集聚性和依存性,ESV热点区和冷点区集聚效果明显,热点区集聚与林地、草地的空间分布相吻合,冷点区集聚与未利用地、耕地和建设用地的空间分布相吻合。(4)受退耕还林还草工程影响,陕北地区中部中等等级和次高ESV分布区域逐渐增大、次热点区空间集聚性逐渐增强,北部次低等级和低等级ESV分布区域逐渐减少、冷点区空间集聚性逐渐减弱。整体而言,陕北地区土地利用类型转移和ESV的增减变化与推行退耕还林还草工程在时间上相呼应、在空间上相匹配,退耕还林还草工程实施使得陕北地区生态环境得到了有效改善,ESV得到了显著提升。 相似文献
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Bacterial blight induced by Xanthomonas campestris pv. malvacearum causes substantial yield losses of cotton in Nigeria annually. A field study was carried out for two seasons to investigate the reaction of a selection of 10 different cotton genotypes to bacterial blight and to examine the relationship between the area under disease progress curve (AUDPC) and the yield of seed cotton in the northeastern cotton region of Nigeria. All 10 genotypes reacted positively to the disease with SAMCOT-13 having the highest incidence particularly at Dowaya and Kem locations during the two seasons. This investigation also revealed that SAMCOT-13 and Ex-Benin had the highest AUDPC while TX-CDP37HH-1-83, TAMCOT CAMD-E and TAMCOT SP-21S had the lowest AUDPC indicating relative susceptibility and resistance, respectively. However, it was observed that TX-CDP37HH-1-83, SAMCOT-11 and Ex-Benin had the highest mean yields of 1441.5 kg/ha and 1494.7 kg/ha at Dowaya, Kem and Ngurore, respectively. The results also show a highly significant (P = 0.01) negative correlation between AUDPC and yield in the three locations. These findings suggest that TX-CDP37HH-1-83, TAMCOT CAMD-E and TAMCOT SP-21S are moderately resistant to the disease in view of their lower AUDPC and are considered promising. 相似文献
10.
Gergely Babocsay 《分类学与生物多样性》2013,11(4):503-514
A study of 353 museum specimens of the Echis coloratus complex from its entire range of distribution revealed an undescribed species in the United Arab Emirates and northern Oman. The results of UPGMA clustering and principal coordinate analysis of 138 male and 142 female specimens yielded for both sexes two major clusters, one with specimens from the UAE and northern Oman and one from southern and western Arabia, the Levant and Egypt. The new species has a longer tail with higher subcaudal counts; the lower prenasal scale is often missing and the upper prenasal is frequently fused with the nasal; the subnasal is often missing or fused with the nasal. The gular scales between the chin‐shield and the preventrals are round or only slightly elongate, not elongate as in Echis coloratus, and their number is higher. Other differences in characters of the gular area indicate a different scale structure of the ventral surface of the head. The new species is allopatric or parapatric with E. coloratus, but sympatric with Echis carinatus sochureki. 相似文献