Adult spawners: A critical period for subarctic Chinook salmon in a changing climate

Concurrent, distribution-wide abundance declines of some Pacific salmon species, including Chinook salmon (Oncorhynchus tshawytscha), highlights the need to understand how vulnerability at different life stages to climate stressors affects population dynamics and fisheries sustainability. Yukon River Chinook salmon stocks are among the largest subarctic populations, near the northernmost extent of the species range. Existing research suggests that Yukon River Chinook salmon population dynamics are largely driven by factors occurring between the adult spawner life stage and their offspring's first summer at sea (second year post-hatching). However, specific mechanisms sustaining chronic poor productivity are unknown, and there is a tremendous sense of urgency to understand causes, as declines of these stocks have taken a serious toll on commercial, recreational, and indigenous subsistence fisheries. Therefore, we leveraged multiple existing datasets spanning parent and juvenile stages of life history in freshwater and marine habitats. We analyzed environmental data in association with the production of offspring that survive to the marine juvenile stage (juveniles per spawner). These analyses suggest more than 45% of the variability in the production of juvenile Chinook salmon is associated with river temperatures or water discharge levels during the parent spawning migration. Over the past two decades, parents that experienced warmer water temperatures and lower discharge in the mainstem Yukon River produced fewer juveniles per spawning adult. We propose the adult spawner life stage as a critical period regulating population dynamics. We also propose a conceptual model that can explain associations between population dynamics and climate stressors using independent data focused on marine nutrition and freshwater heat stress. It is sobering to consider that some of the northernmost Pacific salmon habitats may already be unfavorable to these cold-water species. Our findings have immediate implications, given the common assumption that northern ranges of Pacific salmon offer refugia from climate stressors.     

Lunar periodicity in the spawning of yellowtail damselfish,Microspathodon chrysurus

Synopsis The reproductive behavior of yellowtail damselfish,Microspathodon chrysurus, was studied off the Caribbean coast of Panama to determine if there is a lunar spawning cycle. Male damselfish prepare nest sites on dead coral surfaces within their permanent feeding territories. Spawning occurs at sunrise and lasts for approximately one hour. Males defend the eggs until hatching, which occurs before the morning of the sixth day of incubation. Males spawn only once a day, but may spawn many times within each reproductive phase. Reproductive activity is highest in the time periods from full to new moon. The timing of this lunar cycle differs from those reported for other marine fishes. The spawning pattern is not consistent with common explanations for lunar periodicity that are based on the role of tides or moonlight. Some implications of these results for the organization of tropical reef communities are discussed.     

Diversity and biogeography of a species‐rich ant fauna of the Australian seasonal tropics

Although ants are an ecologically dominant and extensively studied faunal group throughout the tropics, there is a poor understanding of tropical ant diversity and distribution at large spatial scales. Here we use a collection developed from 3 decades of ant surveys to present the first analysis of ant diversity and biogeography of a large tropical region. Our objective was to document the species richness, composition, and biogeographic distributions of the ant fauna of the 400 000 km² “Top End” of Australia's Northern Territory. The known Top End ant fauna comprises 901 native species from 59 genera. The richest genera are Pheidole (90 species), Melophorus (83), Monomorium (83), Camponotus (71), Meranoplus (63), Polyrhachis (57), Rhytidoponera (50), Tetramorium (43), Cerapachys (32), and Iridomyrmex (31). The fauna is the center of diverse radiations within species‐groups of genera such as Meranoplus, Rhytidoponera, and Leptogenys. It also includes IndoMalayan species that have likely bypassed the normal dispersal route into Australia through Cape York Peninsula in North Queensland. Faunistic similarity with other regions of far northern Australia is associated more with rainfall than with geographic proximity. Most (60%) of Top End ant species have not been recorded elsewhere, and, despite uncertainties relating to species delimitation and sampling intensity, this appears to be a credible estimate of the level of endemism. Such exceptionally high endemism can be attributed to the Top End's geographic isolation from other regions of northern Australia with comparably high rainfall.     

Unusual osteolytic defects in ancient South Dakota skulls

Unusual osteolytic defects in eight skulls culled from over 4000 ancient South Dakota burials are presented, discussed briefly, and assigned to what we think is their most likely cause. Because these are collection skeletons, histological and microbiological and microbiological confirmation of interpretations concerning specific lesions are not possible. Corroboration of our opinions has been sought through radiographs and by expert consultation elsewhere. Although our opinions are interpretative and subject to rebuttal, they can serve as a base for future research if and when similar specimens are discovered elsewhere. In addition, these specimens are indicators of other than usual ancient skull pathology from a limited geographic area, representing people who lived there during a known time frame.     

The termite (Isoptera) fauna of a monsoonal rainforest near Darwin, northern Australia

Abstract  Termite species richness, frequency of occurrence and functional diversity at Holmes Jungle Nature Reserve, a monsoon rainforest patch in northern Australia, was investigated at the end of the wet season in 2003. A sampling protocol that employed direct search, soil pits and baiting techniques was used to sample litter, wood, mound, soil and arboreal nest microhabitats for termites. Five species from five genera and three families (Mastotermitidae, Rhinotermitidae and Termitidae) were recorded. This included the first record of Ephelotermes taylori (Hill) from monsoon forest in Australia. The family Termitidae was dominant and represented 70% of termite occurrences. Termites were most frequently encountered in carton runways on tree trunks, followed by lying dead wood and baits. Four nesting habits were represented: arboreal, epigeal, hypogeal and within wood. The arboreal nest-builder Nasutitermes graveolus (Hill) accounted for 61% of termite encounters. Epigeal mound-building species were rare. Wood-feeders were the only trophic group represented. Relatively high activity of Mastotermes darwiniensis Froggatt was recorded at baits within 2.5 months. The low species richness recorded at Holmes Jungle is consistent with the low diversity reported for Australian rainforests generally, but remains relatively depauperate compared with other monsoon forest and savanna habitats of the Northern Territory.     

New species and new record of Tetranychus Dufour from Australia, with a key to the major groups in this genus based on females (Acari: Prostigmata: Tetranychidae)

A new species of spider mite, Tetranychus bunda sp. n., is described and illustrated from Australia. It was found damaging the foliage of Desmodium tortuosum (Sw.) DC. (Fabaceae) in Darwin, Northern Territory. In addition, the geographical range of Tetranychus fijiensis Hirst is extended to include Australia. This species was found in the Northern Territory feeding on frangipani ( Plumeria sp., Apocynaceae), betel palm ( Areca catechu L., Arecaceae) and Macarthur feather palm ( Ptychosperma macarthurii [H. Wendl. ex Veitch] (H. Wendl. ex Hook. f., Arecaceae)). Details of the biology of T. bunda sp. n. and T. fijiensis are given. A key to the major groups of Tetranychus Dufour of the world, based on females, is presented and species known to occur in Australia are outlined.     

Socioecological factors of male chimpanzee migration at Bossou, Guinea

For more than 21 years a small semi-isolated group of wild chimpanzees have been studied at Bossou, Guinea, west Africa. All individuals have been identified since the beginning of the study. Remaining rates of infants (0–3 yr) and juveniles (4–7 yr) in the group were 64–80% for both sexes, however, those of adolescents (8–11 yr) dropped drastically, particularly for males (14%). As a result, most natal males as well as females disappeared before fully maturing. Two male visitors and an immigrant were observed in the group. More adult males than females disappeared from Bossou. Group males could be excluded as the genetic father of an offspring born in the group. From these demographic trends it is highly likely that some of these males emigrated rather than succumbed to sickness and death. It seems likely that they left on their own by choice. The reason for male dispersal is hypothesized to be influenced by intra-group male-male competition and the habitat ecology and structure of Bossou. There are no competitive adjacent groups or predators to prevent males from living alone and males can sire offspring out of their natal group.     

黑腹绒鼠生态学的研究

黑腹绒鼠(Eothenomys melanogaster)是我国南方较常见的鼠种之一,多栖居在海拔较高的山地,且数量较少。我们于1981年1月至1982年1月、1984年7月和11月在浙江西天目山以及1984年3月至12月在金华的北山对黑腹绒鼠作了生态学的调查,现将结果报告如下。     

An 18 million year record of vegetation and climate change in northwestern Canada and Alaska: tectonic and global climatic correlates

We reconstruct long-term vegetation/paleoclimatic trends, spanning the last 18 million years, in Alaska, Yukon and far western Northwest Territories. Twenty-one average percentage spectra for pollen and spores are assembled from eight surface/subsurface sections. The sections are dated independently or by correlation. Pollen and spore ratios indicate the direction of change in vegetation and climatic parameters — growing season temperature (T_est), tree canopy density (C_est) and paludification at study sites (P_est). A global warm peak ca. 15 Ma is shown by the abundance of thermophilous taxa, including Fagus and Quercus. A temperature decline immediately following 15 Ma parallels climatic reconstructions based on marine oxygen isotopes. Subsequent declines correlate to the Messinian event and the onset of late Pliocene-Pleistocene glaciation. After 7 Ma herbs and shrubs become more important elements of the palynological assemblages, suggesting a more continental, colder/drier climate. However, a late Pliocene warm interval is evident. Vegetation/climatic changes during the early to late Miocene show synchrony with, and are most economically attributable to, global events. After 7 Ma, vegetation/climate change is attributed primarily to latest Miocene-to-Pleistocene uplift of the Alaska Range and St. Elias Mts. The continuing influence of global climatic patterns is shown in the late Pliocene warm interval, despite uplift to the south. The opening of the Bering Strait ca. 3 Ma may have moderated the climate in the study area.     

高原鼠兔领域行为时间分配格局及其对风险环境适应的探讨

采用直接观察法测定了高原鼠兔地面、洞道活动时间及进、出洞频率。结果表明,在07：00-18：00,雄性和雌性高原鼠兔平均地面活动时间分别占总活动时间比例的87．09％和85．22％。地面活动时间具有明显的季节性,但两性个体间无显著的差异。繁殖早期,成年雌体地面活动时问显著高于繁殖后期,第2胎幼体地面活动时间显著低于第1胎幼体。不同年龄和性别的高原鼠兔进洞频率存在极显著差异,5月成年雌体进洞频率最高,而成年雄体在4月进洞频率最低。研究结果验证了捕食风险可制约鼠兔属动物领域活动时间分配,高风险环境能增加其利用洞道的时间及频率的特定假设。