Density‐dependent and seasonal variation in reproductive output and sporophyte production in the kelp, Ecklonia radiata

2021 ◽  
Author(s):  
Masayuki Tatsumi ◽  
Christopher J. T. Mabin ◽  
Cayne Layton ◽  
Victor Shelamoff ◽  
Matthew J. Cameron ◽  
...  
2020 ◽  
Vol 28 (02) ◽  
pp. 277-310 ◽  
Author(s):  
ENAHORO A. IBOI ◽  
ABBA B. GUMEL ◽  
JESSE E. TAYLOR

This study presents a new mathematical model for assessing the impact of sterile insect technology (SIT) and seasonal variation in local temperature on the population abundance of malaria mosquitoes in an endemic setting. Simulations of the model, using temperature data from Kipsamoite area of Kenya, show that a peak abundance of the mosquito population is attained in the Kipsamoite area when the mean monthly temperature reaches [Formula: see text]. Furthermore, in the absence of seasonal variation in local temperature, our results show that releasing more sterile male mosquitoes (e.g., 100,000) over a one year period with relatively short duration between releases (e.g., weekly, bi-weekly or even monthly) is more effective than releasing smaller numbers of the sterile male mosquitoes (e.g., 10,000) over the same implementation period and frequency of release. It is also shown that density-dependent larval mortality plays an important role in determining the threshold number of sterile male mosquitoes that need to be released in order to achieve effective control (or elimination) of the mosquito population in the community. In particular, low(high) density-dependent mortality requires high(low) numbers of sterile male mosquitoes to be released to achieve such control. In the presence of seasonal variation in local temperature, effective control of the mosquito population using SIT is only feasible if a large number of the sterile male mosquitoes (e.g., 100,000) is periodically released within a very short time interval (at most weekly). In other words, seasonal variation in temperature necessitates more frequent releases (of a large number) of sterile male mosquitoes to ensure the effectiveness of the SIT intervention in curtailing the targeted mosquito population.


Nature ◽  
1961 ◽  
Vol 192 (4808) ◽  
pp. 1208-1208 ◽  
Author(s):  
C. M. STEWART ◽  
H. G. HIGGINS ◽  
SUE AUSTIN

2010 ◽  
Vol 53 (1) ◽  
pp. 155-163 ◽  
Author(s):  
Graham Forrester ◽  
Lindsay Harmon ◽  
Jason Helyer ◽  
William Holden ◽  
Rebecca Karis

Oikos ◽  
2005 ◽  
Vol 110 (1) ◽  
pp. 155-163 ◽  
Author(s):  
Åke Lindström ◽  
Anders Enemar ◽  
Göran Andersson ◽  
Ted von Proschwitz ◽  
N. Erik I. Nyholm

The Auk ◽  
2010 ◽  
Vol 127 (1) ◽  
pp. 222-231 ◽  
Author(s):  
Kaspar Delhey ◽  
Martín Carrizo ◽  
Lucas C. Verniere ◽  
Bettina Mahler ◽  
Anne Peters

2019 ◽  
Vol 68 (1-2) ◽  
pp. 83-93 ◽  
Author(s):  
Lars Hedenäs ◽  
Irene Bisang

Abstract In the Baltic area, the long-lived dioicous wetland moss Drepanocladus turgescens (T.Jensen) Broth. produces sporophytes rarely and at irregular intervals. Based on surveys of sporophyte occurrences at 13 sites in two regions in northern Gotland (Sweden) during three to five years, we ask: (1) Is sporophyte formation associated with precipitation and a precipitation index that considers the dry periods during July-August of the preceding year, when gametangia are formed and fertilization occurs? (2) Does the estimated spore output suffice for the species’ long-term persistence of the (Northern) European population species? In one of the study regions, where D. turgescens occurs in depressions, sporophyte formation was associated with the two precipitation parameters. In the other study region, with relatively higher precipitation and exposed occurrences on a slightly sloping bedrock with very little accumulated soil, no such association existed. We suggest that this lack of weather effects results from that the exposed rock habitat requires longer continuously wet periods than the depression habitat to allow for gametangia initiation and development, and fertilisation. Average spore production for six spore capsules, from three Gotland localities was 181,000. Based on the sporophyte counts during the survey years, we estimated the total reproductive output as 411.5 million spores in 2013, and 42.5 million in 2015, in the two respective study regions. Taken together with data on haplotype patterns and considering observations on recent colonisations, we argue that such a relatively low and episodic regional spore production is sufficient to maintain global populations of long-lived species, even if these occur in specialized and geographically restricted habitats.


Author(s):  
M.C. Bella ◽  
J.D. Fish

Pectenogammarus planicrurus Reid (Crustacea: Amphipoda) is an inhabitant of unstable gravel beaches. The reproductive output of females of this species was studied at Aberystwyth, on the west coast of Wales. There was marked seasonal variation in the size of eggs: the mean volume of eggs at an early stage of embryonic development ranged from 0·023 mm3 in summer to 0·030 mm3 in winter. Egg size was negatively related to brood size, but seasonal variation in brood size was greater than could be accounted for by egg size alone. Mean brood size ranged from 1·4 eggs in winter to 5·9 eggs in summer. Brood size was also strongly related to female body size, ranging up to 14 eggs in a large female. These findings are discussed in relation to adaptation to interstitial living in coarse intertidal gravels. A model of seasonal variation in reproductive output is suggested in which the importance of point reproductive output is related to the probability of females surviving to produce subsequent broods.


2021 ◽  
Vol 288 (1960) ◽  
Author(s):  
Rachel R. Holser ◽  
Daniel E. Crocker ◽  
Patrick W. Robinson ◽  
Richard Condit ◽  
Daniel P. Costa

All organisms face resource limitations that will ultimately restrict population growth, but the controlling mechanisms vary across ecosystems, taxa, and reproductive strategies. Using four decades of data, we examine how variation in the environment and population density affect reproductive outcomes in a capital-breeding carnivore, the northern elephant seal ( Mirounga angustirostris ). This species provides a unique opportunity to examine the relative importance of resource acquisition and density-dependence on breeding success. Capital breeders accrue resources over large temporal and spatial scales for use during an abbreviated reproductive period. This strategy may have evolved, in part, to confer resilience to short-term environmental variability. We observed density-dependent effects on weaning mass, and maternal age (experience) was more important than oceanographic conditions or maternal mass in determining offspring weaning mass. Together these findings show that the mechanisms controlling reproductive output are conserved across terrestrial and marine systems and vary with population dynamics, an important consideration when assessing the effect of extrinsic changes, such as climate change, on a population.


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