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181.
Detecting Population Declines over Large Areas with Presence-Absence, Time-to-Encounter, and Count Survey Methods 总被引:4,自引:0,他引:4
JACOB F. POLLOCK† 《Conservation biology》2006,20(3):882-892
Abstract: Ecologists often discount presence-absence surveys as a poor way to gain insight into population dynamics, in part because these surveys are not amenable to many standard statistical tests. Still, presence-absence surveys are sometimes the only feasible alternative for monitoring large areas when funds are limited, especially for sparse or difficult-to-detect species. I undertook a detailed simulation study to compare the power of presence-absence, count, and time-to-encounter surveys to detect regional declines in a population. I used a modeling approach that simulates both population numbers and the monitoring process, accounting for observation and other measurement errors. In gauging the efficacy of presence-absence surveys versus other approaches, I varied the number of survey sites, the spatial variation in encounter rate, the mean encounter rate, and the type of population loss. My results showed that presence-absence data can be as or more powerful than count data in many cases. Quantitative guidelines for choosing between presence-absence surveys and count surveys depend on the biological and logistical constraints governing a conservation monitoring situation. Generally, presence-absence surveys work best when there is little variability in abundance among the survey sites, the organism is rare, and the species is difficult to detect so that the time spent getting to each survey site is less than or equal to the time spent surveying each site. Count surveys work best otherwise. I present a case study with count data on the Northern Flicker ( Colaptes auratus ) from the North American Breeding Bird Survey to illustrate how the method might be used with field-survey data. The case study demonstrates that a count survey would be the most cost-effective design but would entail reduction in the number of sites. If this site reduction is not desirable, a presence-absence survey would be the most cost-effective survey. 相似文献
182.
Mace R 《Behavioral ecology and sociobiology》1996,38(2):75-81
Demographic data from 848 Gabbra households are used to examine the relationships between herd size and reproductive success
in relation to sex, in a traditional, pastoralist population. The number of camels in the household herd has a significant
positive effect on the reproductive success of both men and women, although the effect of wealth is greater for men, as predicted
from evolutionary theory. The greater the number of elder brothers a man has, the lower his reproductive success, as a result
of a smaller initial herd and a later age at marriage. This is not true for women –number of elder sisters does not have a
measurable effect on a woman’s fertility, although it does have a small, negative effect on the size of her dowry. These results
are interpreted as competition between same-sex siblings for parental investment, in the form of their father’s herd, which
is more intense between sons than daughters as parental investments are greatest in males.
Received: 30 June 1995/Accepted after revision: 23 October 1995 相似文献
183.
We tested several hypotheses to explain low between-year territory fidelity in a breeding population of yellow-headed blackbirds (Xanthocephalus xanthocephalus). During a 5-year study the population of territorial males declined by two-thirds and some of the marshes that supported territories significantly deteriorated. Individual males held territories and bred for an average of 1.9 years. Of males that bred for at least 2 years, 30% skipped owning a territory in the study area during at least 1 year of their breeding lifetimes. Our information suggests that they may have bred outside of the area in those years. Of males with territories in two or more breeding seasons, 60% changed breeding marshes at least once. Males changed territories during 42.9% of between-year opportunities to do so. We found no support for the hypotheses that male yellow-headed blackbirds: (1) are more likely to move when territory density is low; (2) are likely to abandon territories that are deteriorating; or (3) change territories to improve their reproductive success. We suggest three non-mutually exclusive explanations for the yellow-headed blackbird's weak site fidelity: (1) it is a response to habitat deterioration and to other factors that may be causing the population's decline; (2) the males, being migratory, make fresh settlement decisions each year after they arrive on the breeding grounds in the general vicinity of their previous year's breeding; (3) yellow-headed blackbirds may have evolved in, and be adapted to, highly unstable habitats, moving frequently in response to changes in local breeding site conditions.
Correspondence to: L.D. Beletsky 相似文献
184.
Howard H. Whiteman John D. Krenz Raymond D. Semlitsch 《Behavioral ecology and sociobiology》2006,60(1):52-61
The study of reproductive isolation as a prerequisite to sympatric speciation has been limited by the focus on species that
have already experienced such isolation. However, a complete understanding of how such processes evolve depends on observing
taxa before they complete the speciation process. We studied the potential for sexual isolation in the polyphenic mole salamander,
Ambystoma talpoideum, using a series of laboratory and field experiments. This species consists of aquatic paedomorphic adults and terrestrial
metamorphic adults which are exhibited by both sexes and which mate in the same aquatic habitat. Previous field studies on
this species suggested that intermorph breeding would be less common during the winter months, because paedomorphic adults
begin breeding in early autumn and thus may have less energy available for reproduction in the winter. Laboratory experiments
conducted during the winter showed that the mating behavior of paedomorphic males occurred at a much lower frequency than
that of metamorphic males. In contrast, field experiments that best mimicked natural conditions revealed symmetric intermorph
breeding and included multiple paternity shared among males of each morph. This and other studies suggest that there is little
evidence of sexual isolation among morphs based on behavioral interactions alone. However, the potential for partial isolation
still occurs because of temporal and spatial differences in the frequencies of each morph in nature. Our results suggest that
further studies on this system, and other similar polyphenisms, may provide valuable insight into the mechanisms that underlie
the evolution of reproductive isolation. 相似文献
185.
SHIRLI BAR-DAVID‡ DAVID SALTZ† TAMAR DAYAN AMIR PERELBERG AMIT DOLEV 《Conservation biology》2005,19(1):131-138
Abstract: Because most reintroduced species are rare, data on their dynamics are scarce. Consequently, reintroduction programs often rely on data from other species or captive populations to project the performance of the reintroduced population in the wild. We compared the reproductive success and survival of a Persian fallow deer ( Dama mesopotamica ) population reintroduced in Israel over the first 5 years of the project with the survival and reproduction parameters estimated while planning the reintroduction. In addition, we compared the actual growth of the wild population with the growth originally projected by a computer model in the original reintroduction program. We monitored 74 radio-collared individuals (57 females and 17 males) released semiannually 1996–2001. Survival during the first year after release was lower than later years (0.90 and 0.82 versus 0.95 and 0.88, for females and males, respectively). Such an impact was not anticipated in the original plan, but overall survival was higher than originally projected. As assumed in the reintroduction program, reproductive success improved significantly with time since release and overall, was higher than expected. The mean number of animals released annually was lower than planned. Overall, the growth of the reintroduced population was slower than projected, but the deviation was close to confidence limits and the pattern similar. After 5 years it appears that the original time frame of 8–10 years for project completion can be met or at worst will cause a 1-year delay. Over the short term of 5 years, projection models in reintroduction programs are useful tools for assessing the sustained use of the breeding core, depicting the dynamics of the population in the wild, providing a relatively accurate time frame for the successful completion of the project, and assessing project success. 相似文献
186.
Walter R. Tschinkel 《Behavioral ecology and sociobiology》1998,43(4-5):247-257
Many benefits and risks of cooperative colony founding (pleometrosis) have been identified, but rarely have the proximate
factors that lead to association been considered. This study examined the choices queens make during the first few hours after
mating, and some of the correlates of those choices. Queens had a strong affinity for preformed holes in the soil and readily
used these as their initial founding chambers. This affinity was so strong that in a field experiment, the dispersion pattern
of preformed holes controlled the final dispersion of colony-founding queens. Attraction to partially formed holes is thus
an important cause of pleometrosis. The excavation of complete founding chambers incurred no measurable cost on the subsequent
reproductive output of queens, suggesting that the primary benefit of using preformed holes is to remove the queen quickly
from exposure to predation and desiccation. In the field, pairs of queens offered five equivalent preformed holes in soil
were more likely to share the same hole if the holes were shallow and close together. In these experiments, queens modified
preformed soil holes so that the test holes were no longer equivalent, causing the choice of queen and hole to become confounded.
Laboratory experiments in plaster arenas with unmodifiable holes confirmed the field experiments: queens were more likely
to share a hole when the holes were shallow than when they were deep. Because queens entering adequately deep holes seldom
reemerged, this suggested that the likelihood of sharing increased with increasing contact between queens, that is, when queens
were readily and frequently detected. Such contacts will also predict the future competitive environments to be experienced
by incipient colonies, and may temper the tendency of queens to associate. However, experiments in which queens were exposed
to high and low densities before pairing in the choice arenas failed to show an effect on the choice to join the resident
queen. Queens that joined a resident queen differed in their robustness from queens that did not join. Queens choosing their
own partners did no better reproductively than those assigned partners at random. Overall, this study suggests that (1) newly
mated queens are under strong selection to leave the soil surface and do so by using any available holes, whether dug by another
queen or of some other origin; (2) they are attracted to other queens, and are more likely to cofound as contact with the
potential cofoundress becomes more frequent and (3) they choose whether or not to cofound partly on the basis of their own
reproductive characteristics.
Received: 20 November 1997 / Accepted after revision: 14 March 1998 相似文献
187.
This study is about 16 policy-induced innovation networks on climate change adaptation, i.e., subsidised multi-actor networks that are initiated by research institutes and formed around a particular real-life problem aiming at joint development, test, and implement adaptation measures. The political-administrative context is Germany, and the institutional context is a joint research framework in which each network works independently on a particular topic, but remains bound to the principle of practical and solution-oriented research carried out in close partnership between scientific and extra-scientific actors. Our objective is to provide empirical insights into the processes and outcomes of such networks and to systematically analyse the networks’ collaboration success and its influencing factors. To this end, collaboration success is operationalised as a three-dimensional metric including (1) the practitioners’ satisfaction with the cooperation, (2) their perceived learning effects, and (3) their perceived implementation capacity. Results show a decreasing level of success throughout the three dimensions and particularly a gap between knowledge acquisition and learning on the one hand and implementation, i.e., transforming the knowledge into action, on the other. While the positive relationship between these dimensions is confirmed, results of correlation analysis highlight the importance of repeated participation, appropriate information management, and inclusive as well as responsive network practices. We discuss the results against our existing knowledge on multi-actor collaborative research and deduce (methodological) lessons learnt as well as future research needs. 相似文献
188.
Ståle Liljedal Geir Rudolfsen Ivar Folstad 《Behavioral ecology and sociobiology》2008,62(11):1805-1811
In postcopulatory sexual selection both sperm competition and cryptic female choice are considered to be important selective
agents, but their relative importance for male fertilization success has received little attention. We tested whether sperm
quality, male spawning coloration, male heterozygosity, and genetic overlap with the female explained a male’s fertilization
success in controlled in vitro fertilization competition trials between equal numbers of sperm from pairs of male Arctic charr
(Salvelinus alpinus), an external fertilizer. Offspring were genotyped to determine each males’ share of paternity. The velocity of a male’s
sperm relative to the velocity of the competing male’s sperm was the best predictor of male fertilization success. Yet, sperm
velocity was not related to spawning coloration or male heterozygosity. In fact, the most brightly colored male in a pair
had the lowest fertilization probability. This could result from cryptic female choice for pale males, but might rather be
a result of paler males producing more competitive sperm than more colored males. Furthermore, the more microsatellite alleles
a male shared with the female relative to the competing male, the higher fertilization success he had. We argue that this
latter may be an effect of assortative cryptic female choice, which might prevent hybridization with sympatric Arctic charr
morphs or one form of kin selection. 相似文献
189.
处理好发展经济与保护环境的关系,尤其是项目建设与节能减排的关系,这是实现可持续发展的关键。近年来,一些地区和城市,把节能减排作为促进科学发展的重要手段,推进经济可持续发展,取得了可喜的成绩。但是,也存在着不少障碍。在肯定对节能减排初见成效的基础上,对节能减排障碍进行了剖析,为了加大节能减排与环境保护力度,阐述了国家节能减排的行业政策,提出了节能减排的十项路径选择。 相似文献