A refined model of body mass and population density in flightless birds reconciles extreme bimodal population estimates for extinct moa

Latham, M. Cecilia; Wilmshurst, Janet M.; Forsyth, David M.; Gormley, Andrew M.; Pech, Roger P.; Perry, George L.; Wood, Jamie R.

doi:10.1111/ecog.04917

Cited by 15 publications

(12 citation statements)

References 58 publications

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“…We then calculated theoretical equilibrium population densities (D, km -2 ) based on the following: = 10 4.196−0.740log 10 2 ⁄ [eq 3] for mammalian herbivores (M = body mass in g), where dividing by 2 predicts for females only (i.e., assumed 1:1 sex ratio) (Damuth 1981). For large, flightless birds (i.e., Genyornis and Dromaius) (Latham et al 2020), we applied:…”

Section: Estimating Demographic Rates and Population Data As Input Pamentioning

confidence: 99%

“…For birds, we used an optimization of the objective function based on age at first breeding ( α , estimated as shown below), adult survival ( s ad , estimated as shown below), and the allometric constant for birds ( Dillingham et al, 2016 ) a rT = 1.107:

We then calculated theoretical equilibrium population densities ( D , km −2 ) based on the following:

for mammalian herbivores ( M = body mass in g), where dividing by two predicts for females only (i.e., assumed 1:1 sex ratio) ( Damuth, 1981 ). For large, flightless birds (i.e., Genyornis and Dromaius ) ( Latham et al, 2020 ), we applied:

and:

for omnivorous birds (i.e., Alectura ) ( Juanes, 1986 ) where M is in g. For mammalian carnivores, we applied:

( M in kg), which we derived from Stephens et al, 2019 . There were no specific invertivore or taxonomically specific equations to estimate D ; however, we determined that the equation for the fitted 97.5 percentile in mammalian carnivores:

Stephens et al, 2019 provided is a reasonable D for female Tachyglossus = 9.9 km −2 .…”

Section: Choice Of Species and Body Mass Distributionmentioning

confidence: 99%

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Relative demographic susceptibility does not explain the extinction chronology of Sahul’s megafauna

Bradshaw

Johnson

Llewelyn

et al. 2021

eLife

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The causes of Sahul's megafauna extinctions remain uncertain, although several interacting factors were likely responsible. To examine the relative support for hypotheses regarding plausible ecological mechanisms underlying these extinctions, we constructed the first stochastic, age-structured models for 13 extinct megafauna species from five functional/taxonomic groups, as well as eight extant species within these groups for comparison. Perturbing specific demographic rates individually, we tested which species were more demographically susceptible to extinction, and then compared these relative sensitivities to the fossil-derived extinction chronology. Our models show that the macropodiformes were the least demographically susceptible to extinction, followed by carnivores, monotremes, vombatiform herbivores, and large birds. Five of the eight extant species were as or more susceptible than the extinct species. There was no clear relationship between extinction susceptibility and the extinction chronology for any perturbation scenario, while body mass and generation length explained much of the variation in relative risk. Our results reveal that the actual mechanisms leading to the observed extinction chronology were unlikely related to variation in demographic susceptibility per se, but were possibly driven instead by finer-scale variation in climate change and/or human prey choice and relative hunting success.

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Section: Estimating Demographic Rates and Population Data As Input Pamentioning

confidence: 99%

We then calculated theoretical equilibrium population densities ( D , km −2 ) based on the following:

and:

for omnivorous birds (i.e., Alectura ) ( Juanes, 1986 ) where M is in g. For mammalian carnivores, we applied:

Stephens et al, 2019 provided is a reasonable D for female Tachyglossus = 9.9 km −2 .…”

Section: Choice Of Species and Body Mass Distributionmentioning

confidence: 99%

Relative demographic susceptibility does not explain the extinction chronology of Sahul’s megafauna

Bradshaw

Johnson

Llewelyn

et al. 2021

eLife

View full text Add to dashboard Cite

show abstract

“…However, recent reconstructions of the ecological function of extinct species underpinned by modelling, inferences from allometric scaling and palaeoecological data demonstrate new capabilities in understanding the roles of extinct species (e.g. Latham et al, 2019;Novak et al, 2018;Pires, Guimarães, Galetti, & Jordano, 2018). High resolution reconstructions of extinct species' seed interactions based on species density, distribution and diet may be a promising future research avenue.…”

Section: Developing a More Comprehensive Understanding Of Functionamentioning

confidence: 99%

The forgotten fauna: Native vertebrate seed predators on islands

et al. 2020

Self Cite

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Human colonization of islands has resulted in the reduction or loss of many native species, and the introduction of non‐native species, producing novel ecosystems. The impacts of these changes on mutualistic plant–animal interactions have received considerable attention, but the potential effects on some antagonistic interactions, such as seed predation, are less thoroughly understood, and often overlooked. Using three archetypal island groups—New Zealand, the Mascarenes and Hawaiʻi—we compare the taxonomic richness and functional diversity of vertebrate seed predators from prehuman and contemporary ecosystems. We scored species on several traits relevant to seed predation, then clustered species into functionally similar groups using hierarchical clustering. These archipelagos once supported between 19 and 24 species of exclusively avian seed predators (representing two to four orders) ranging from large, flightless herbivores to small, volant finches and parrots. Following human arrival, 63%–89% of these species went extinct, and between 12 and 23 non‐native seed predators were introduced. Contemporary seed predator faunas consist of between 14 and 26 species (representing six to seven orders), dominated by non‐native granivorous birds and omnivorous mammals. Our results reveal several examples in which non‐native species may be functionally similar to extinct seed predators, but most non‐native species are functionally different from extinct species, and therefore may be introducing novel seed predation pressures for insular ecosystems. Mammalian seed predators are especially functionally different from the native avian seed predators, as their teeth and widespread habitat distribution allow them to destroy a more diverse range of seeds, including the largest seeds. We highlight the need to understand how these altered seed predator communities are affecting native plant populations, particularly in the context of reduced pollination and seed dispersal. More broadly, we argue that antagonistic interactions are an integral part of any ecosystem, and therefore must be understood if we are to achieve more holistic restoration frameworks for insular ecosystems. A free Plain Language Summary can be found within the Supporting Information of this article.

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“…) 2 ⁄ [eq 3] for mammalian herbivores (M = body mass in g), where dividing by 2 predicts for females only (i.e., assumed 1:1 sex ratio) [22]. For large, flightless birds (i.e., Genyornis and Dromaius) [23], we applied: = 10 ,.#-'!.. (log !"…”

Section: Appendix S2 Estimating Demographic Rates and Population Datmentioning

confidence: 99%

“…Stochastic demographic models can therefore potentially test the relative contribution of the following five mechanisms regarding the putative drivers of the megafauna extinctions in Sahul (summarized in Fig. 1): (i) There is a life history pattern in which the slowestreproducing species succumbed first to novel and efficient human hunting [1,22,23]. This hypothesis assumes that human hunting, even if non-selective, would differentially remove species that were more demographically sensitive to increased mortality arising from novel human exploitation [24].…”

Section: Introductionmentioning

confidence: 99%

Relative demographic susceptibility does not explain the extinction chronology of Sahul’s megafauna

Bradshaw

Johnson

Llewelyn

et al. 2020

Preprint

View full text Add to dashboard Cite

The causes of Sahul's megafauna extinctions remain uncertain. To test hypotheses regarding plausible ecological mechanisms underlying these extinctions, we constructed the first stochastic, age-structured models for 13 extinct megafauna species from five functional/taxonomic groups (+ 8 extant species for comparison). Perturbing specific demographic rates individually, we tested which species were more demographically susceptible to extinction, and then compared these relative sensitivities to the fossil-derived extinction chronology. The macropodiformes were the most resilient to extinction, followed by carnivores, monotremes, vombatiform herbivores, and large birds. Five of the eight extant species were as or more susceptible than were the extinct species. There was no clear relationship between extinction susceptibility and the extinction chronology for any perturbation scenario, but body mass and generation length explained much of the variation in relative risk. Our models reveal that the actual mechanisms leading to extinction were unlikely related to variation in demographic susceptibility per se.

show abstract

A refined model of body mass and population density in flightless birds reconciles extreme bimodal population estimates for extinct moa

Cited by 15 publications

References 58 publications

Relative demographic susceptibility does not explain the extinction chronology of Sahul’s megafauna

Relative demographic susceptibility does not explain the extinction chronology of Sahul’s megafauna

The forgotten fauna: Native vertebrate seed predators on islands

Relative demographic susceptibility does not explain the extinction chronology of Sahul’s megafauna

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