Population demography and sex ratio in a Neotropical damselfly (Odonata: Coenagrionidae) in Costa Rica

1989 ◽  
Vol 5 (2) ◽  
pp. 159-171 ◽  
Author(s):  
Linda D. Hamilton ◽  
Robert D. Montgomerie
Keyword(s):  
Costa Rica ◽  
Sex Ratio ◽  
Survival Rates ◽  
Small Population ◽  
Mature Adults ◽  
Egg Formation ◽  
Significant Difference ◽  
Biased Sex Ratio ◽  
Males And Females ◽  
Prereproductive Period

ABSTRACTThroughout the latter part of the dry season (January-April) of 1985 and 1986, we studied the demography of mature adults in a small population of Argia chelata along a stream at Monteverde, Costa Rica. Males defended sunlit spots along the stream between 1030 h and 1400 h central standard time each day and females visiting these sunlit spots were soon mated. By individually marking all mature adults in the population we found that there was no significant difference between the sexes in daily survival rates (0.85 for males and 0.86 for females). Lifetime mating success was positively correlated with longevitiy in both males and females but the ability of males to obtain a mate appeared to be independent of age.Although the sex ratio at emergence was 1:1, that of mature adults at the stream was strongly male-biased (87% male), perhaps as a result of a longer or more risky prereproductive period in females related to the costs of egg formation. We argue that the strongly male-biased sex ratio has important effects on the mating system of this species in that the male contact-guards the female for the entire oviposition period each day. Although this limits each male to mating with one female per day, it probably ensures that the male will fertilize most of the eggs laid by the female that day.

The spatial pattern of a Juniperus communis var. depressa population on a continental dune in subarctic Québec, Canada

1999 ◽  
Vol 29 (4) ◽  
pp. 446-450 ◽  
Author(s):  
Gilles Houle ◽  
Mario Duchesne
Keyword(s):  
Sex Ratio ◽  
Nearest Neighbor ◽  
Dispersion Pattern ◽  
Neighbor Distance ◽  
Juniperus Communis ◽  
Biased Sex Ratio ◽  
Males And Females ◽  
Nearest Neighbor Distance ◽  
Population Dispersion ◽  
Crown Size

We performed a nearest-neighbor analysis to determine the population dispersion pattern and the association between males and females in a Juniperus communis L. var. depressa Pursh population occupying a continental dune in subarctic Quebec, Canada. The overall dispersion pattern was contagious, and males (or females) were proportionately as likely to have a male as they were to have a female nearest neighbor. Crown size was positively related to nearest-neighbor distance for the male-male comparison only, suggesting a somewhat stronger intrasex competition between males. Nearest-neighbor distance increased with crown size (significantly related to age) suggesting a change in the intensity of aggregation with age possibly related to self-thinning. Higher mortality as a result of stronger male-male competition could explain the female-biased sex ratio and the absence of spatial segregation between sexes. The overall contagious dispersion pattern in the population may be related to the fact that most seed cones fall directly underneath the mother plant. Birds can eat the cones of J. communis and thus disperse seeds. However, these seeds are deposited in clumps, a process that may also explain contagion within the population.

scholarly journals PERBANDINGAN JENIS KELAMIN DAN DIMORFISME SEKSUAL PADA PERTUMBUHAN IKAN GURAMI (Osphronemus goramy) SERTA IMPLIKASINYA TERHADAP STRATEGI SELEKSINYA

2017 ◽  
Vol 11 (4) ◽  
pp. 307 ◽  
Author(s):  
Sularto Sularto ◽  
Rita Febrianti ◽  
Suharyanto Suharyanto
Keyword(s):  
Sex Ratio ◽  
Standard Length ◽  
Adult Size ◽  
Male Fish ◽  
Male And Female ◽  
Fish Breeding ◽  
Significant Difference ◽  
Different Populations ◽  
Males And Females ◽  
Number Of Males

Ikan gurami (Osphronemus goramy Lac.) pada ukuran dewasa memiliki bentuk morfometrik yang khas khususnya pada ikan jantan, sehingga dapat dibedakan antara ikan jantan dan betina. Ikan gurami jantan memiliki dahi menonjol dan bibir tebal. Penelitian ini bertujuan untuk mengevaluasi rasio kelamin dan perbedaan performa pertumbuhan antara jantan dan betina. Ikan uji yang digunakan adalah empat populasi ikan gurami yang berbeda yaitu: Kalimantan Selatan, Jambi, Majalengka, dan Tasikmalaya. Penelitian dilaksanakan di Balai Penelitian Pemuliaan Ikan (BPPI), Sukamandi pada bulan Juni 2014 sampai dengan bulan Juli 2015. Hewan uji yang digunakan adalah benih ikan gurami keturunan galur murni berasal dari Kalimantan Selatan, Jambi (strain Batanghari), Majalengka, dan Tasikmalaya. Perawatan telur, pemeliharaan benih, dan pembesaran menggunakan prosedur operasional standar BPPI tentang pemeliharaan ikan gurami. Pemeliharaan ikan gurami dilakukan selama 14 bulan. Hasil penelitian menunjukkan bahwa berdasarkan jenis kelaminnya jumlah ikan gurami betina (67,3%-80,7%) lebih banyak dibandingkan dengan jumlah jantannya (19,3%-32,7%). Setelah mencapai ukuran > 300 g terdapat perbedaan pertumbuhan antara ikan jantan dan betina (P<0,05) yakni jantan tumbuh lebih cepat dibandingkan betina pada semua populasi yakni berkisar antara 4,74%-5,67% untuk karakter panjang standar, dan 14,10%-16,52% untuk karakter bobot. Hal tersebut menunjukkan bahwa ikan gurami memiliki dimorfisme pertumbuhan. Oleh karena itu, ketika dilakukan seleksi berdasarkan pertumbuhan 10% terbaik didapatkan ikan jantan 55%-80% lebih banyak dibandingkan ikan betina (20%-45%).Adult size of giant gouramy (Osphronemus goramy, Lac.) has a distinctive shape of morphometric particularly in male fish, making it easy to distinguish between male and female fishes. Giant gouramy males have a prominent forehead and thick lips. This study aimed to determine sex ratios and differences in growth performance between males and females. This study used 4 progenies of giant gouramy seed from four different populations, namely: Kalimantan, Jambi, Majalengka, and Tasikmalaya, aged 14 months. Eggs incubations,seed maintenance and grow-out were conducted using Standard Operational Procedures of Research Institute for Fish Breeding (RIFB) about the rearing of giant gouramy. Seed rearing were carried out for 14 months. The results showed that, based upon the sex ratio, the number of female was more than the number of males, contituting females 67.3%–80.7% and males from 19.3% to 32.7% of populations. After reaching the size of > 300 g there were a significant difference in growth between males and females (P <0.05), in which males grew faster than females in all populations between 4.74%–5.67% for the standard length and 14.10%–16.52% for the weight characters. IThis result indicated that giant gouramy have growth dimorphism.Therefore, when the selection conducted based on the best growth of top 10%, it was found that the number of male composing 55%–80% was higher than the number of female which only accounted for 20%–45%.

scholarly journals Biased sex-ratio in woodland grouse population of the Tatra National Park, suggested by molecular sexing of non-invasive samples

2021 ◽  
Vol 63 (2) ◽  
pp. 129-136
Author(s):  
Anna SANTOREK ◽  
◽  
Tomasz ZWIJACZ-KOZICA ◽  
Beata DULISZ ◽  
Dorota MERTA ◽  
...  
Keyword(s):  
Sex Ratio ◽  
National Park ◽  
Large Deviation ◽  
Survival Rates ◽  
Molecular Sexing ◽  
Black Grouse ◽  
In The Wild ◽  
Biased Sex Ratio ◽  
Tatra National Park ◽  
Genetic Assessment

Sex ratio (ratio between the number of male and female individuals in a population) is an important factor contributing to the survival rates of the population in wild. Imbalanced sex ratio is often the cause of diminished survival rates of endangered species. The analysis of DNA collected through noninvasive methodologies effectively allows to monitor populations of rare species or species that are difficult to observe in the wild. Such method was used to determine the sex ratio in populations of the capercaillie (Tetrao urogallus) and black grouse (Lyrurus tetrix) in the Tatra National Park. We collected over 250 samples (mostly excrement) in the area of the Tatra National Park and identified species via microsatellite genotyping and determined the sex using fragments of the CHD gene. We found that the majority of the samples belonged to male specimens irrespective of the species suggesting a large deviation from an equal sex ratio in wild populations of capercaillie and black grouse in the Tatra National Park. Our results point out the fundamental contribution of genetic assessment of sex ration to monitor the viability of both species in the Tatra National Park.

A PRELUDE ON THE BIOLOGY OF PUNTIUS AMPHIBIUS

2017 ◽  
Vol 4 (1) ◽  
pp. 69-72
Author(s):  
Munisha Murali S ◽  
Sheeba S
Keyword(s):  
Sex Ratio ◽  
Feeding Habits ◽  
Monsoon Season ◽  
Gut Content ◽  
Significant Difference ◽  
Active Feeding ◽  
Food And Feeding ◽  
Males And Females ◽  
Relationship Of ◽  
Somatic Index

Knowledge on fish biology is essential for improving aquaculture. The present study was focused on the biology of Puntiusamphibius. The fishes were collected from a freshwater body in parlance known as “Arappa”, located in Thalikulam at Thrissur district in Kerala. This water body is in the vicinity of the sea anddebouches into the marine during monsoon season. In the present investigation 106 fishes were collected during March to August 2006. The study revealed that there was no significant difference observed among the length weight relationship of males and females. Composition of gut content showed that it is a selectivefeeder of Bacillariophyceae and a pronounced omnivore. The gastro-somatic index of female and male was high during May indicating the active feeding during breeding.The sex ratio between males and females was variable and female dominated over males. The fecundity of fish was proportional to the weight of the ovary. Gonado-somatic index was comparatively high during spawning seasons. This is a preliminary lesson on the reproductive biology and certain distinctive characters such as length-weight and food and feeding habits of Puntius amphibius.

scholarly journals Sex ratio of breeding Common toads (Bufo bufo) – influence of survival and skipped breeding

2010 ◽  
Vol 31 (4) ◽  
pp. 509-524 ◽  
Author(s):  
Thomas Madsen ◽  
Jon Loman
Keyword(s):  
Sex Ratio ◽  
Deterministic Model ◽  
Breeding Site ◽  
Breeding Population ◽  
Bufo Bufo ◽  
Adult Males ◽  
Breeding Sites ◽  
Lower Survival Rate ◽  
Biased Sex Ratio ◽  
Males And Females

AbstractAnuran sex ratio at breeding sites is typically male biased. Such sex ratios may be due to poor female survival, to females not breeding as frequently as males and/or to males becoming sexually mature earlier than females. In the present study, the first two factors are analyzed in a common toad (Bufo bufo) population in southern Sweden. Toads were captured, marked and recaptured at the breeding site during 5 years. Within season capture patterns were analyzed using the Jolly-Seber model and among-year captures using the Closed robust design model. Population estimates of males and females yielded an among year variation in breeding population sex ratio, ranging from 16% to 34% females. On average, 41% (proportion adult alive but not breeding) of the females skipped breeding seasons, whereas the corresponding estimate for males was less than 5%. Yearly survival averaged 42% for adult female and 63% for adult male toads. First year adult males and females had a lower survival rate than older toads. Our results demonstrate that both a female biased mortality rate and a higher proportion of skipped breeding in females contribute to the observed male biased sex ratio. However, a deterministic model suggests other factors may also be involved to obtain this degree of male biased sex ratio, the most likely being that females mature at a later age than male toads.

scholarly journals Willow Flycatcher Nonbreeding Territory Defense Behavior in Costa Rica

The Condor ◽  
2007 ◽  
Vol 109 (2) ◽  
pp. 475-480 ◽  
Author(s):  
Mark K. Sogge ◽  
Thomas J. Koronkiewicz ◽  
Charles Van Riper ◽  
Scott L. Durst
Keyword(s):  
Costa Rica ◽  
Random Noise ◽  
Sexually Dimorphic ◽  
Territorial Defense ◽  
Defense Behavior ◽  
Territory Defense ◽  
Significant Difference ◽  
Males And Females ◽  
Willow Flycatcher ◽  
Study Sites

Abstract We studied the intraspecific territorial defense behavior of wintering Willow Flycatchers (Empidonax traillii) in Costa Rica using a randomized playback experiment that exposed male and female birds to recordings of Willow Flycatcher songs and calls, Lesser Ground Cuckoo (Morococcyx erythropygius) vocalizations, and random noise. Flycatchers of both sexes responded most strongly to simulated conspecific territory intrusion, and the agonistic behaviors that we observed were similar to those seen during natural intraspecific encounters in winter. Both males and females engaged in song and aggressive behaviors in defense of territories, and there was no significant difference between the sexes in scored agonistic responses. The similarity between the sexes in intraspecific territorial defense behaviors and aggressiveness may account for both sexes of flycatchers using the same habitats at our study sites in Costa Rica, and wintering females defending territories against males. The Willow Flycatcher, a sexually monomorphic species, differs in this way from a number of sexually dimorphic passerines, in which behaviorally dominant males occur in more optimal winter habitats.

Reproductive characteristics of the sand sole Pegusa lascaris (Soleidae), from the eastern-central Atlantic

2008 ◽  
Vol 88 (3) ◽  
pp. 629-635 ◽  
Author(s):  
José G. Pajuelo ◽  
José M. Lorenzo
Keyword(s):  
Sexual Dimorphism ◽  
Sex Ratio ◽  
Reproductive Biology ◽  
Standard Length ◽  
Spawning Season ◽  
Significant Difference ◽  
Males And Females ◽  
First Maturity ◽  
Central Atlantic ◽  
Size At First Maturity

The reproductive biology of 1318 sand sole, Pegusa lascaris, was investigated. This species is a gonochoristic species with no evidence of sexual dimorphism. The overall sex-ratio was 1 male to 0.92 females. Females predominate in the larger size intervals, with a significant difference in mean standard length and range between sexes. Size at first maturity for males and females is attained at 17.2 and 17.7 cm standard length, respectively. Vitellogenesis does not begin synchronously for all females, as a consequence the spawning season appears to be continuous. In each female spawning takes place in two batches which are spawned mainly in spring and autumn, indicating that fish are serial synchronous spawners.

scholarly journals Morphometric characteristics of crayfish, Cherax gherardiae, from Maybrat, West Papua, Indonesia

2018 ◽  
Vol 26 (4) ◽  
pp. 223-230
Author(s):  
Yulianus Sedik ◽  
Dominggus Rumahlatu ◽  
Bambang Irawan ◽  
Agoes Soegianto
Keyword(s):  
Sexual Dimorphism ◽  
Sex Ratio ◽  
Carapace Length ◽  
Condition Factor ◽  
Carapace Width ◽  
Allometric Growth ◽  
Morphometric Characteristics ◽  
Significant Difference ◽  
West Papua ◽  
Males And Females

Abstract The objectives of this study were to determine the length-weight relationships (LWRs), chelae length (ChL)-width (ChW) relationships, carapace length (CL)-width (CW) relationships, sexual dimorphism, and condition factor (K) of Cherax gherardiae from Maybrat, West Papua Indonesia. The sex ratio of C. gherardiae was found to be 1.04:1. The LWRs for males, females, and all individuals were W = 0.225L1.96, W = 0.181L2.02, and W = 0.187L2.03, respectively. Males and females exhibited negative allometric growth (b<3). There was no significant difference in lengths between males and females; however, the weight of males was greater than that of females. The K values for males, females, and all individuals were 3.17, 3.09, and 3.13, respectively. The ChL of the crayfish ranged from 1.0 to 7.5 cm, and the ChW ranged from 0.4 to 2.5 cm. The CL of crayfish ranged from 1.6 to 6.0 cm, and the CW ranged from 0.6 to 4.1 cm. Males had longer chelae and carapaces than did females. There was no significant difference in chelae width or carapace width between males and females. The ChL-ChW relationships for males, females, and all individuals were ChW = 0.312ChL + 0.260, ChW = 0.397ChL - 0.050, and ChW = 0.345ChL + 0.119, respectively. The CL-CW relationships for males, females, and all individuals were CW = 0.750CL-0.955, CW = 0.526CL - 0.178, and CW = 0.635CL-0.543, respectively.

scholarly journals Demography of the enigmatic low phase in a cyclic lemming population

2021 ◽  
Author(s):  
Dominique Fauteux ◽  
Gilles Gauthier
Keyword(s):  
Sex Ratio ◽  
Reproductive Potential ◽  
Indirect Evidence ◽  
Adult Males ◽  
Density Dependent ◽  
Live Trapping ◽  
Biased Sex Ratio ◽  
Males And Females ◽  
Cyclic Populations

Abstract Deciphering the mechanism behind the lack of growth during the prolonged low abundance phase of cyclic populations represents a major challenge due to the lack of data. However, long-term capture-mark-recapture datasets can help resolve this question through demographic analyses. We analysed the demography and movements of cyclic brown lemmings on Bylot Island, Canada, with a 16-yr (2004-2019) live-trapping program and looked for inversely density-dependent factors that could contribute to a prolonged low phase. We found that the proportion of females in the population was inversely density-dependent with a strong male-biased sex ratio at low densities but not at high densities. In contrast, survival of adult females was higher than adult males, but both had lower survival at low densities than at high ones. Distances moved by both adult males and females were density-dependent, and proportion of females in reproductive condition was weakly density-dependent. Individual body condition, measured as monthly change in body mass, was not density-dependent. Overall, the strong malebiased sex ratio at very low densities suggests a loss of reproductive potential due to the rarity of females and appears to be the most susceptible demographic factor that could contribute to the prolonged low phase in cyclic brown lemmings. What leads to this sexbias in the first place is still unclear, but indirect evidence suggests that this may be due to a higher vulnerability of nesting females to predation in winter than males.

EFFECT OF NON-GENETIC AND GENETIC FACTORS ON BIRTH WEIGHT OF MENGALI SHEEP OF BALOCHISTAN

2011 ◽  
Vol 1 ◽  
pp. 121-128
Author(s):  
Muhammad Masood Tariq ◽  
Keyword(s):  
Birth Weight ◽  
Sex Ratio ◽  
Least Squares ◽  
Genetic Factors ◽  
Factors Affecting ◽  
Experimental Station ◽  
Female Sex ◽  
Significant Difference ◽  
Males And Females ◽  
Male To Female

Data on birth weight of 2377 lambs obtained from 581 dams and 56 sires of Mengali sheep born during 2005 and 2009 were recorded and analyzed to identify the factors affecting birth weight of Mengali lambs. Mengali flocks were kept under semi-intensive condition in four stations at three different locations (Experimental Station Center for Advanced studies in Vaccinology and Biotechnology (CASVAB), University of Balochistan, (ESC), Quetta, Killi Hassni, Quetta; Khadkucha, Mastung and Peer Wala (Mal), Nushki). The lambing occurred spring and autumn, however majority of the Mengali sheep (85 %) lambed during spring between (February and March months). Among the total lambs born, the male to female sex ratio was 49.43: 50.57 respectively and shown no significant difference between two sexes. The overall least-squares means for birth weight of males and females pooled over parity and type of birth were 3.61±0.36 and 3.48±0.39 kg respectively

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