Geology, geomorphology and climate change

Boelhouwers, Jan; Meiklejohn, Ian; Holness, Stephen

doi:10.18820/9781928357063/04

Cited by 28 publications

(43 citation statements)

References 31 publications

(79 reference statements)

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“…Hall 2002;Boelhouwers et al 2008) and ecosystem distribution (e.g. Dispersal capabilities may be variable within species and strongly dependent on environmental conditions, especially for organisms that undergo SPATIAL GENETIC STRUCTURE AND WIND PROPERTIES 189 passive and wind-assisted dispersal.…”

Section: Discussionmentioning

confidence: 99%

Plant dispersal in the sub‐Antarctic inferred from anisotropic genetic structure

et al. 2011

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Climatic conditions and landscape features often strongly affect species' local distribution patterns, dispersal, reproduction and survival and may therefore have considerable impacts on species' fine-scale spatial genetic structure (SGS). In this study, we demonstrate the efficacy of combining fine-scale SGS analyses with isotropic and anisotropic spatial autocorrelation techniques to infer the impact of wind patterns on plant dispersal processes. We genotyped 1304 Azorella selago (Apiaceae) specimens, a wind-pollinated and wind-dispersed plant, from four populations distributed across sub-Antarctic Marion Island. SGS was variable with Sp values ranging from 0.001 to 0.014, suggesting notable variability in dispersal distance and wind velocities between sites. Nonetheless, the data supported previous hypotheses of a strong NW-SE gradient in wind strength across the island. Anisotropic autocorrelation analyses further suggested that dispersal is strongly directional, but varying between sites depending on the local prevailing winds. Despite the high frequency of gale-force winds on Marion Island, gene dispersal distance estimates (σ) were surprisingly low (<10 m), most probably because of a low pollen dispersal efficiency. An SGS approach in association with isotropic and anisotropic analyses provides a powerful means to assess the relative influence of abiotic factors on dispersal and allow inferences that would not be possible without this combined approach.

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Section: Discussionmentioning

confidence: 99%

Plant dispersal in the sub‐Antarctic inferred from anisotropic genetic structure

et al. 2011

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“…Marion Island has experienced at least five episodes of glaciation during the Late Quaternary (McDougall et al, ). The extent of glaciation during the LGM (~35–11,000 years before present) is uncertain, but it is believed to have been widespread and covered almost the entire island (Boelhouwers et al, ; Hall, ; Hall et al, ). Several prominent areas on the island, however, lack evidence of glaciation and may have served as ice‐free refugia; these sites are largely coastal (Boelhouwers et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…The extent of glaciation during the LGM (~35–11,000 years before present) is uncertain, but it is believed to have been widespread and covered almost the entire island (Boelhouwers et al, ; Hall, ; Hall et al, ). Several prominent areas on the island, however, lack evidence of glaciation and may have served as ice‐free refugia; these sites are largely coastal (Boelhouwers et al, ). Palynological studies indicate that the same plants found on Marion Island today, including Azorella , were present during interglacial periods (Schalke & Van Zinderen Bakker, ; Scott, ; Scott & Hall, ).…”

Section: Discussionmentioning

confidence: 99%

“…Spatial genetic patterns in A. selago on Marion Island are consistent with a history of survival in a southeast refugium during glacial periods (see Mortimer et al, for similar suggestions for the mite Halozetes fulvus ). Genetic diversity, measured as expected heterozygosity and allelic richness, is highest in the southeast, where the Feldmark Plateau, a refugial area during the LGM, is located (Boelhouwers et al, ). From the southeast, colonization of the rest of the island could have occurred after glacial retreat via consecutive founder events, which would result in lower genetic diversity along the direction of population expansion.…”

Section: Discussionmentioning

confidence: 99%

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The influence of landscape, climate and history on spatial genetic patterns in keystone plants (Azorella) on sub‐Antarctic islands

et al. 2019

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The distribution of genetic variation in species is governed by factors that act differently across spatial scales. To tease apart the contribution of different processes, especially at intermediate spatial scales, it is useful to study simple ecosystems such as those on sub‐Antarctic oceanic islands. In this study, we characterize spatial genetic patterns of two keystone plant species, Azorella selago on sub‐Antarctic Marion Island and Azorella macquariensis on sub‐Antarctic Macquarie Island. Although both islands experience a similar climate and have a similar vegetation structure, they differ significantly in topography and geological history. We genotyped six microsatellites for 1,149 individuals from 123 sites across Marion Island and 372 individuals from 42 sites across Macquarie Island. We tested for spatial patterns in genetic diversity, including correlation with elevation and vegetation type, and clines in different directional bearings. We also examined genetic differentiation within islands, isolation‐by‐distance with and without accounting for direction, and signals of demographic change. Marion Island was found to have a distinct northwest–southeast divide, with lower genetic diversity and more sites with a signal of population expansion in the northwest. We attribute this to asymmetric seed dispersal by the dominant northwesterly winds, and to population persistence in a southwestern refugium during the Last Glacial Maximum. No apparent spatial pattern, but greater genetic diversity and differentiation between sites, was found on Macquarie Island, which may be due to the narrow length of the island in the direction of the dominant winds and longer population persistence permitted by the lack of extensive glaciation on the island. Together, our results clearly illustrate the implications of island shape and geography, and the importance of direction‐dependent drivers, in shaping spatial genetic structure.

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“…In diurnal frost environments we believe that the time-scale at which climate drivers affect the ground frost conditions is in the order of hours to days, rather than seasonal or annual. At this time-scale synoptic weather conditions dominate the temporal variability in ground temperature as superimposed on the seasonal shift in ground energy budget (Outcalt 1971;Boelhouwers et al 2008).…”

Section: Introductionmentioning

confidence: 99%

The effect of synoptic scale weather systems on sub‐surface soil temperatures in a diurnal frost environment: preliminary observations from sub‐antarctic marion island

Nel

Boelhouwers

Zilindile

2009

Geografiska Annaler: Series A, Physical Geography

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. Marion Island in the South Indian Ocean has a maritime climate dominated by diurnal frost processes in the landscape. We test the hypothesis that synoptic time‐scale measurements are essential in understanding the drivers of diurnal frost processes. Preliminary results from automated microclimate measurements in a polar desert habitat show that diurnal soil surface temperatures on Marion Island are influenced by a complex interaction of radiation balance, air mass circulation, cloud cover and snow. The passage of synoptic scale weather systems influences soil thermal characteristics through changes in dominance of the radiation budget. Soil frost on Marion appears to be dependent on clear skies, while synoptic weather systems affect the duration and intensity of soil frost processes and non‐radiative heat fluxes. Air circulation patterns at Marion Island influence diurnal scale temperature fluctuations and its direct and indirect interactions with ecosystem processes. The data suggest that in a maritime sub‐Antarctic environment the climatic drivers of soil frost occur at a finertemporal resolution than for seasonal and permafrost environments and needs to be measured at a diurnal time‐scale to be meaningful.

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Geology, geomorphology and climate change

Cited by 28 publications

References 31 publications

Plant dispersal in the sub‐Antarctic inferred from anisotropic genetic structure

Plant dispersal in the sub‐Antarctic inferred from anisotropic genetic structure

The influence of landscape, climate and history on spatial genetic patterns in keystone plants (Azorella) on sub‐Antarctic islands

The effect of synoptic scale weather systems on sub‐surface soil temperatures in a diurnal frost environment: preliminary observations from sub‐antarctic marion island

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