Effects of Interspecific Competition for Food in Breeding Blue and Great Tits

10.2307/4061 ◽  
1981 ◽  
Vol 50 (2) ◽  
pp. 375 ◽  
Author(s):  
Edward O. Minot
Keyword(s):  
Interspecific Competition ◽  
Competition For Food

Competition for food and allied phenomena in sheep-blowfly populations

1950 ◽  
Vol 234 (610) ◽  
pp. 77-174 ◽  
Keyword(s):  
South Africa ◽  
Interspecific Competition ◽  
Larval Growth ◽  
Pupal Stage ◽  
Growth Characteristics ◽  
Controlling Factor ◽  
Primary Group ◽  
Additional Food ◽  
Adverse Conditions ◽  
Competition For Food

Competition for food among larval populations of sheep blowflies constitutes an important factor limiting the general fly population in nature. Both intra- and interspecific competition take place on carrion. In South Africa the main species of flies concerned are Lucilia sericata Mg., L. cuprina Wied., Chrysomyia chloropyga Wied., C. albiceps Wied., and C. marginalis Wied. The degree to which these species suffer loss of population from the effects of intra- and interspecific competition on a carcass is determined mainly by their inherent growth characteristics and by the degree to which they are adapted to withstand the adverse conditions engendered by overcrowding of the larval populations on the available food supply. In this paper the species listed above have been examined on the basis of rigid experimental tests to ascertain their respective responses to competition of varying degrees of intensity. It has become evident that the species of Lucilia , which are the most important in relation to strike in sheep, are better adapted than are their competitors to withstand the effects of straightforward competition for food. Adaptations to meet adverse conditions consist of the rapidity of larval growth and the time at which the most rapid growth period occurs, the ability to form viable pupae at a comparatively low final growth weight and a general reduction in the size of the individuals in a population in favour of an increased total number of survivors. In these respects Lucilia spp. are able to achieve greater success than the Chrysomyia species. They are therefore always more successful under adverse conditions. An exception is found in the case of C. albiceps in which the larvae have predatory habits and are therefore able to destroy competitors on the carcass. C. albiceps is always characterized by a lower field population than occurs with the other species and is therefore limited in its usefulness as a controlling agent. It is more exposed to the attack of parasites and predators during the vulnerable pupal stage and the general fly population is thereby very considerably reduced during the summer months. In South Africa, blowflies are seasonal in their appearance on carrion and can be divided into two well-defined groups of summer feeders and winter feeders. These two groups correspond with the classification into secondary and primary blowflies respectively. Overlapping between the two groups occurs at the times when the populations of both are at their lowest ebb. Competition for food is therefore less intense between the primary and secondary groups than it is between species occurring within the same group. Secondary fly populations cannot therefore materially affect those of the primary group. For this reason and for others which concern its growth characteristics, Chrysomyia marginalis cannot appreciably influence populations of Lucilia and is therefore not a controlling factor for the latter as has been claimed. When Lucilia and C. chloropyga occur together on a carcass, the former is always able to survive and to reduce the population of the latter species. Competition in field populations of blowfly larvae is regulated by a number of factors, some of which have no direct connexion with the fly populations themselves. The quantity of carrion available, for example, is governed by the population dynamics of the animals from which it is derived and by those of the predatory and scavenging groups which prey upon them. During the 20 or 30 years over which the blowfly problem has become more acute in South Africa, it is noteworthy that a considerable change has occurred in the balance between predator and prey populations due to the activity of man. The latter have increased as the former have gradually been destroyed because of their depredations on domestic stock. The amount of carrion, derived from small animals, has therefore increased, providing additional food for blowfly larvae. From experiments and from field observations it is clear that competition for food can never serve as an efficient controlling factor for blowfly populations. This is especially true for populations of the important primary species ( Lucilia spp.). Competition acts to produce fluctuations in the populations of flies subjected to it, so that certain years are marked by abnormally large populations of adult flies which produce an increased incidence of strike in sheep. Such years are well known to farmers as ‘bad fly seasons’. Reduction of blowfly breeding grounds by means of the destruction of carcasses in the field is not likely to prove efficacious. It is clear that we require to know a great deal more about the relationships between the populations of flies, their environment, their natural controlling factors and their fluctuations as related to the factors which influence competition in the field before we can hope to evolve any satisfactory measures which are designed as a frontal attack on the blowflies themselves.

Competition for Food Between Redside Shiners (Richardsonius balteatus) and Rainbow Trout (Salmo gairdneri) in Two British Columbia Lakes

1961 ◽  
Vol 18 (2) ◽  
pp. 203-220 ◽  
Author(s):  
R. E. Johannes ◽  
P. A. Larkin
Keyword(s):  
British Columbia ◽  
Rainbow Trout ◽  
Interspecific Competition ◽  
Stomach Contents ◽  
Salmo Gairdneri ◽  
Interspecific Aggression ◽  
Large Numbers ◽  
Competition For Food ◽  
Biological Environment ◽  
Richardsonius Balteatus

The distribution, movements, behaviour and food of trout and shiners in Paul and Pinantan Lakes were studied to determine the items and mechanisms of interspecific competition between them. Data from recent years were compared with data for years when trout alone inhabited the lakes.No interspecific aggression was observed. The possibility that the two species were competing for space was discounted. Stomach contents of shiners in Pinantan Lake revealed a marked qualitative diurnal food cycle. In Paul Lake, shiners have drastically reduced the Gammarus population relative to its pre-shiner abundance, forcing trout, as well as the shiners themselves, to shift their diets to other foods. This overgrazing was caused by the concentration of large numbers of shiners over the shoals where Gammarus are also present in their highest concentrations, and the ability of shiners to pursue food deeper into the weeds and to graze an area more thoroughly than trout. In Pinantan Lake, shiners have apparently reduced the density of Daphnia to a point where trout are unable to feed on them as rapidly as in pre-shiner years. The ability of both species to utilize many types of food tends to reduce the intensity of competition.The study demonstrates how false implications may arise from an appraisal of competition not initiated until after the effects of competition have been observed. If observations had not been made on Paul Lake until after competition had been observed, the importance of Gammarus as an item of competition would probably have been overlooked and the whole competitive relationship misconstrued.Environmental factors and behaviour were shown to be important influences on the dynamics of competition. The physical and biological environment and the distribution and behaviour of competitors may be in states of continual flux in which case the niches of the competitors cannot be considered constant.

scholarly journals Helminth community structure and diet of three Afrotropical anuran species: a test of the interactive-versus-isolationist parasite communities hypothesis

Web Ecology ◽  
2011 ◽  
Vol 11 (1) ◽  
pp. 11-19 ◽  
Author(s):  
G. C. Akani ◽  
L. Luiselli ◽  
C. C. Amuzie ◽  
G. N. Wokem
Keyword(s):  
Interspecific Competition ◽  
Dietary Habits ◽  
Parasite Community ◽  
Helminth Community ◽  
Parasite Communities ◽  
Anuran Species ◽  
Infection Parameters ◽  
Parasitological Survey ◽  
Competition For Food ◽  
Species Specific

Abstract. The interactive-versus-isolationist hypothesis predicts that parasite communities should be depauperated and weakly structured by interspecific competition in amphibians. A parasitological survey was carried out to test this hypothesis using three anuran species from Nigeria, tropical Africa (one Bufonidae; two Ranidae). High values of parasite infection parameters were found in all three species, which were infected by nematodes, cestodes and trematodes. Nonetheless, the parasite communities of the three anurans were very depauperated in terms of number of species (4 to 6). Interspecific competition was irrelevant in all species, as revealed by null models and Monte Carlo permutations. Cluster analyses revealed that, in terms of parasite community composition, the two Ranidae were similar, whereas the Bufonidae was more different. However, when prevalence, intensity, and abundance of parasites are combined into a multivariate analysis, each anuran species was clearly spaced apart from the others, thus revealing considerable species-specific differences in terms of their parasite communities. All anurans were generalists and probably opportunistic in terms of dietary habits, and showed no evidence of interspecific competition for food. Overall, our data are widely consistent with expectations driven from the interactive-versus-isolationist parasite communities hypothesis.

scholarly journals Temperature niche difference and interspecific competition determine the parapatric distribution of two congeneric species in Diaphanosoma

2020 ◽  
Author(s):  
Ping Liu ◽  
Jiaying Pan ◽  
Jianhao Lin ◽  
Zhanming Wen ◽  
Qi Huang ◽  
...  
Keyword(s):  
Interspecific Competition ◽  
Critical Role ◽  
Thermal Adaptation ◽  
Congeneric Species ◽  
Coexistence Theory ◽  
Stable Temperature ◽  
Food Conditions ◽  
Parapatric Distribution ◽  
Competition For Food ◽  
Food Niche

Abstract Background Diaphanosoma excisum and D. dubium are parapatrically distributed in tropical and subtropical waters, and rarely coexist at local communities in the transition between tropics and subtropics. According to Janzen’s hypothesis and the modern coexistence theory, the specific thermal adaptation and strong interspecific competition between the two congeneric species are assumed to result in their range limits. To explore the mechanisms underlying such parapatric distribution, we modeled their current geographic distribution, and compared temperature niche difference and fitness inequality in interspecific competition with their representative clones.Results The species distribution modeling showed that the two Diaphanosoma species had significantly divergent climate niches. Their life history parameters in monocultures also demonstrated as stable temperature niche difference, while D. excisum had higher fitness than D. dubium in dimension of food niche. The competition experiments revealed a strong exploitative competition between the two species, and D. excisum was the superior competitor, and excluded D. dubium in all the competition experiments within overlapping temperature niche regardless of food conditions.Conclusions Our results suggest that stable temperature niche difference overcoming interspecific competition for food plays a critical role in shaping Diaphanosoma species range.

scholarly journals Climate, ecological release and bill dimorphism in an island songbird

2013 ◽  
Vol 9 (3) ◽  
pp. 20130118 ◽  
Author(s):  
Russell Greenberg ◽  
Raymond M. Danner
Keyword(s):  
Interspecific Competition ◽  
Positive Temperature ◽  
Island Size ◽  
Ecological Release ◽  
Size Dimorphism ◽  
Island Populations ◽  
Song Sparrows ◽  
Summer Heat ◽  
High Summer Temperature ◽  
Competition For Food

Sexual size dimorphism is expected to be more pronounced in vertebrates on islands, particularly in trophic characters, as a response to decreased interspecific competition for food. We found (based on measurements of 1423 museum specimens) that bill size dimorphism was greater in island than mainland populations of song sparrows. However, dimorphism varied among islands and was positively correlated with high summer temperature and island size. Island song sparrow bills follow the overall positive temperature bill size relationship for California song sparrows, which includes larger bills on large, warmer islands. Large bills dissipate more heat and may be an adaptation to summer heat stress. Dimorphism increases because the slope for males is greater than females. Thus, the greater magnitude of bill dimorphism on islands with warmer summers may result from males experiencing greater thermal stress during territorial activity, creating different thermal optima. In contrast, bill dimorphism was unrelated to climate on the mainland. We hypothesize that reduced interspecific competition releases island populations from a constraint so that sex-specific physiological optima can be achieved, whereas mainland birds are constrained.

Food of Two Cohabiting Tide-Pool Cottidae

1971 ◽  
Vol 28 (6) ◽  
pp. 928-932 ◽  
Author(s):  
Royden Nakamura
Keyword(s):  
Interspecific Competition ◽  
West Coast ◽  
Tide Pool ◽  
The West ◽  
Chironomid Larvae ◽  
Food Items ◽  
Interspecific Differences ◽  
Relative Composition ◽  
Competition For Food ◽  
And Behavior

The organisms found on seven dates in the stomachs of two cottids (Oligocottus maculosus and O. snyderi) cohabiting four rocky tide pools on the west coast of Vancouver Island were the same except for one minor item. Quantitatively, a number of differences were present. For the major food items, the interspecific differences in relative composition of the diets were greatest for amphipods and copepods. Lesser differences are seen for annelids, isopods, and chironomid larvae. However, these were more likely a reflection of differences in microhabitat and behavior rather than interspecific competition for food.

Comparison of the Diets of Nestling Cattle Egrets and Intermediate Egrets in the Hunter Valley, New-South-Wales

1989 ◽  
Vol 16 (4) ◽  
pp. 395 ◽  
Author(s):  
GS Baxter ◽  
PG Fairweather
Keyword(s):  
Interspecific Competition ◽  
New South ◽  
New South Wales ◽  
Dietary Overlap ◽  
Bulk Weight ◽  
South Wales ◽  
Competition For Food ◽  
Breeding Seasons

The foods of Ardeola ibis coromandus and Egretta intermedia plumijera were determined from boluses regurgitated by chicks. There were 61 boluses collected from A. ibis and 33 from E. intermedia over four breeding seasons. A. ibis ate orthopteran insects (66% bulk weight) with fewer vertebrates (23%). E. intermedia relied on vertebrates (69%), mainly fish (58%), but also ate orthopterans (22%). Each species was largely opportunistic in its feeding but probably selected different habitats in which to forage. From the small dietary overlap revealed in this study, we conclude that interspecific competition for food was unlikely during the 1985-1987 breeding seasons.

Instar Succession, Vertical Distribution, and Interspecific Competition Among Four Species of Chaoborus

1977 ◽  
Vol 34 (1) ◽  
pp. 113-118 ◽  
Author(s):  
John C. H. Carter ◽  
Judith K. Kwik
Keyword(s):  
Life Cycle ◽  
Vertical Distribution ◽  
Interspecific Competition ◽  
River System ◽  
Spatial Separation ◽  
Oligotrophic Lakes ◽  
Intense Competition ◽  
Chaoborus Punctipennis ◽  
Competition For Food

Of four highly oligotrophic lakes of the Matamek River System, Quebec, Lac à la Croix contains Chaoborus punctipennis and C. trivittatus, Lac Gallienne C. americanus, Lac Randin C. americanus and C. trivittatus, and Lac Méchant C. flavicans and C. trivittatus. The instars are all planktonic except instars I–III of C. trivittatus in Lac à la Croix. All species have a 1-yr life cycle except C. americanus in Lac Gallienne which has a 2-yr cycle. The cycles of C. trivittatus in lacs Randin and Méchant are out of phase by 1 mo or more with those of C. americanus and C. flavicans, respectively. Seasonal increases in length occurred in most instars except those of C. punctipennis in Lac à la Croix. Both species in Lac à la Croix made fairly extensive diurnal migrations but in lacs Gallienne and Méchant all species remained near the surface. Intense competition for food is considered the most likely cause of seasonal or spatial separation of instars of similar size in all lakes.

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