Niche overlap in allotopic and syntopic populations of sexually interacting ground‐hopper species

Abstract There is accumulating evidence that sexual interactions among species (reproductive interference) could have dramatic effects for species’ coexistence. It has been shown that the fitness of individuals can be substantially reduced as a consequence of reproductive interference. This might subsequently lead to displacement of a species (sexual exclusion). On the other hand, some evolutionary and ecological mechanisms might enable species to coexist, such as the divergence of mate recognition systems (reproductive character displacement), habitat partitioning, clumped dispersion patterns or different colonization capabilities. We have previously shown that the two ground‐hopper species Tetrix subulata and Tetrix ceperoi interact sexually in the laboratory as well as in the field. At sites where both species co‐occur niche overlap was high, suggesting that coexistence is maintained by different niche breadths rather than by habitat partitioning. To test the hypothesis that habitat partitioning does not contribute to species’ coexistence, we examined whether allotopic and syntopic populations of these two species differ in niche overlap (competitive release). Our results show that niche overlap is higher in syntopic than in allotopic populations, suggesting that the site‐specific habitat structure (heterogeneity) has a stronger influence on microhabitat utilization than the presence of heterospecifics. Hence, our data do not support the hypothesis that habitat partitioning plays a substantial role for the coexistence of these sexually interacting species.     

Do ecologically close species shift their daily activities when in sympatry? A test on chamois in the presence of mouflon

Temporal partitioning of daily activities between species may promote coexistence within animal communities by reducing behavioural interference, particularly when species highly overlap in the use of space and resources. Such a strategy may be used by Alpine chamois (Rupicapra rupicapra rupicapra) when in the presence of mouflon (Ovis gmelini musimon × Ovis sp.), an introduced highly gregarious species with a broader ecological niche, overlapping with that of chamois. Using simultaneous monitoring of 29 Global Positioning System‐collared chamois and 12 mouflon, we assessed the temporal variation in activity patterns of chamois amongst two subpopulations: one without mouflon and one with mouflon, during January and August, which are the two most extreme periods of spatial overlap of mouflon with chamois distribution. Substantial differences in activity patterns between chamois and mouflon were observed (mean 13.8 ± 10.5% in January and 10.6 ± 11.6% in August). More subtle differences appeared between both subpopulations of chamois and persisted, regardless of the spatial overlap with mouflon (3.2 ± 1.8% in January and 2.6 ± 1.5% in August), thus highlighting that there is no behavioural interference from mouflon on chamois. Our findings suggest that the temporal partitioning of daily activities between chamois and mouflon, although probably a result of species‐specific adaptations to environmental conditions, may contribute to their coexistence. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 621–626.     

白颈长尾雉与白鹇秋冬季空间生态位比较

2008年9月-2009年2月,在江西官山国家级自然保护区对白颈长尾雉(Syrmaticus ellioti)和白鹇(Lophura nycthemera)及其栖息地生态因子进行调查,通过8个资源轴分析了2个种的多维生态位宽度、重叠及种间竞争.结果表明,白鹇和白颈长尾雉综合空间生态位宽度分别仅为0.268和0.294;白鹇的海拔和坡度空间生态位大于白颈长尾雉.而白颈长尾雉的坡向生态位宽度大于白鹇,在其他资源轴上二者接近;白颈长尾雉和白鹇的栖息地生态位相似性为0.425,竞争系数为0.584,竞争比较激烈.应加强低海拔地区植被及水源的保护,减少人为干扰.     

红树林群落通过淹水时间及海水盐度的生态位分化实现物种共存

红树林是生长在热带、亚热带海湾河口潮间带的受到周期性海水淹浸的木本植物群落, 红树植物如何适应潮间带环境、实现多物种分离共存一直是研究的热点。生态位理论是解释群落物种共存的重要理论和方法之一, 而幼苗是种群更新的基础。因此, 本研究选取海南岛分布较广的6种红树植物幼苗, 通过人工控制海水盐度、淹没时间和光照强度模拟不同的潮间带环境, 构建了一个微型的红树林小群落。通过测定这6种幼苗在不同控制环境中的净光合速率, 统计分析幼苗在海水盐度、淹水时间和光照强度3种资源条件下的生态位宽度、生态位重叠和生态位偏离程度, 尝试阐述红树植物在潮间带中分离共存的机制。结果表明: 在淹水方面, 6种幼苗的生态位宽度最大的为白骨壤(Avicennia marina) (0.956), 角果木(Ceriops tagal) (0.906)最小; 白骨壤、桐花树(Aegiceras corniculatum)和红海榄(Rhizophora stylosa)的生态位重叠度较高, 秋茄(Kandelia obovata)、海莲(Bruguiera sexangula)和角果木的生态位重叠度较高。生态位分离程度反映出在理论生态位中心是12 h/d的物种中, 白骨壤(0.698)适应淹水的范围较大, 在理论生态位中心是8 h/d的物种中秋茄(0.185)适应淹水的范围较大, 在理论生态位中心是4 h/d的物种中海莲(0.115)适应淹水的范围较大。在盐度资源方面, 生态位宽度最大的为白骨壤(0.987), 秋茄(0.496)最小; 白骨壤、桐花树和红海榄的生态位重叠度高, 海莲和角果木的生态位重叠度高, 秋茄与其他物种的生态位重叠度均不高。生态位分离程度反映出理论生态中心为20的物种中白骨壤(4.357)适应盐度的范围较大, 理论生态位中心是10的物种中角果木(10.594)适应盐度的范围较大。在光照资源方面, 生态位宽度最大的为角果木(0.995), 白骨壤(0.828)最小; 6种红树植物的生态位重叠度均较高; 生态位分离程度反映出理论生态中心为100%光照的物种中红海榄(23.138)适应光照的范围较大, 理论生态位中心是80%光照的物种中角果木(12.522)适应光照的范围较大。结合各物种在淹水、盐度和光照资源上的生态位分析, 可以看出它们在淹水和盐度资源上的生态位分化相对较早且明显, 各物种占据不同的淹水和盐度生态位, 生态位重叠程度相对较低, 对淹水和盐度资源的竞争较弱, 进而实现在潮间带中的分离共存; 而在光照资源上的生态位分化相对较晚且不明显, 多数为阳生植物, 生态位重叠程度较高, 对光照的竞争相对较强。     

Habitat use by sympatric populations of Pseudomys novaehollandiae and Mus domesticus in coastal heathland

Abstract Patterns of habitat use by Pseudomys novaehollandiae and Mus domesticus were investigated on a 6. 8 ha area of coastal heathland, almost five years after it last burned in Myall Lakes National Park. One hundred and fifty-one trap stations were positioned on 17 traplines across a mosaic of interlocking macrohabitats. This pattern was a consequence of the site's topography and to a lesser extent fire history. Multivariate statistical procedures were employed to identify those microhabitat parameters that contribute to both individual species’ habitat use and the partitioning of habitat to reduce competition for space. Trapping results show P. novaehollandiae to be almost three times as abundant as M. domesticus at this time, although M. domesticus does show strong regional, and hence local, fluctuations in abundance over time. Both species exhibit habitat selection (P< 0. 05) with individuals preferring dry, tall closed heath and open heathland habitats. Immature P. novaehollandiae (< 15 g) were found mostly in short dense wet heath and may have been dispersing. Species exhibit high between-habitat overlap using Pianka's formula (0. 88). This overlap is substantially reduced within macrohabitats (0. 28), when trap stations are considered as resource states, suggesting a considerable degree of microhabitat separation at the trap station level. Discriminant function and multiple regression analyses identify microhabitat selection that is not strongly focused, suggesting both species to be spatial generalists. Elevation was selected as the most significant variable in these analyses and represents a soil moisture gradient that determines changes in the floristic and structural components of the biotic environment. No single habitat variable was found to explain within-habitat separation convincingly, however, when a factor analysis of habitat variables was used to produce a reduced three-dimensional factor space the outcome was marked. The 95% confidence envelopes for the distribution of each species show an extremely low overlap in factor space, with a zero overlap in the X-Y plane and less than 1% overlap in theY-Z plane. Differential micro-habitat selection does produce effective habitat partitioning, thus facilitating coexistence of these two species. We suspect this occurs primarily by M. domesticus altering habitat selection. There is evidence to suggest that M. domesticus acts as a fugitive species occupying resource niches left vacant by P. novaehollandiae and other small mammal species coexisting on the study area.     

Effectiveness of size frequency distributions in regulating intraspecific spatial overlap of stream insects

Spatial niche breadth and overlap of size groups of four species of epilithic stream insects were studied to determine if broad size frequency distributions serve to reduce intraspecific competition for space. Mean niche overlap decreased with greater breadth of size frequency distributions for only one species (Baetis intercalaris) and did not vary in relation to population density. Similarly, the ratio of the probabilities of intergroup and intragroup encounter did not vary as a function of the breadth of size frequency distributions. Therefore, it was concluded that changes in size frequency distribution have a minimal effect on intraspecific competition for space among epilithic species. It was suggested that observed size frequency distributions may be more a function of extant environmental conditions (temperature and flow) than of previous or extant intraspecific competition.     

Differences in Species Composition and Feeding Ecology of Catostomid Fishes in Two Distinct Segments of the Missouri River, North Dakota, U.S.A.

In 1997 and 1998, we sampled the Missouri River, North Dakota to determine if anthropogenic disturbances had influenced catostomid species composition and feeding ecology. We compared two distinct river segments, the Missouri River between the mouth of the Yellowstone River and Lake Sakakawea (the Yellowstone–Sakakawea segment (YSS)), a moderately altered segment and the Missouri River between Garrison Dam and Lake Oahe (the Garrison–Oahe segment (GOS)), a highly altered segment. The segments exhibited greatly different sucker communities. Bigmouth buffalo, Ictiobus cyprinellus, smallmouth buffalo, Ictiobus bubalus, and river carpsucker, Carpiodes carpio, represented 94% of the sucker catch in the YSS, whereas in the GOS, white sucker, Catostomus commersoni, and longnose sucker, Catostomus catostomus, constituted 98% of the sucker catch. In the YSS, high zooplankton densities led to greater sucker zooplanktivory and food niche overlap than in the GOS. Intense anthropogenic disturbances to the GOS are associated with the differences in sucker species composition, prey density and composition, and sucker feeding ecology between the two segments.     

浙江披山海域主要鱼类时空生态位

依据2015年11月(秋)、2016年2月(冬)、5月(春)、8月(夏)4个航次的渔业资源底拖网调查数据,运用相对重要性指数(IRI)、Shannon指数和Pianka指数对浙江披山海域主要鱼类的时空生态位宽度和重叠进行分析,并结合冗余分析和种间竞争系数研究了主要鱼类间的竞争共存关系及生态位分化.结果 表明:研究期间共...     

Climatic niche partitioning following successive invasions by fruit flies in La Réunion

1. Biological invasions have profound effects on community structure. The community composition following invasions can be influenced by the habitat diversity and the species' responses to abiotic factors. 2. We evaluated the tolerance to climatic factors and analysed the field distribution of four polyphagous fruit flies (Diptera: Tephritidae) of La Réunion Island (three exotic species that successively invaded the island and the endemic species Ceratitis catoirii) in order to evaluate the opportunities of coexistence by niche differentiation. 3. Atmospheric humidity and immersion in water in the laboratory greatly influence the survival of fruit fly pupae. While C. catoirii and C. rosa are very sensitive to desiccation, C. capitata and especially Bactrocera zonata are relatively tolerant. B. zonata also tolerated immersion in water much longer than did C. rosa and C. catoirii, that in turn were more resistant than C. capitata. Overall, field distributions agree with the predictions based on this study of humidity combined with previous data on the effects of temperature. 4. Climatic niche partitioning promotes coexistence between some but not all pairs of invasive species. Thus, C. rosa can coexist with both C. capitata and B. zonata at the regional scale, while climatic niches are not different enough to promote coexistence of the latter two species. The endemic species has no private climatic niche either and this now very rare species could be in the process of extinction. 5. By promoting coexistence or not, climatic diversity in invaded areas can directly affect the community composition following invasions.