6 research outputs found
The effects of coastal lowland instability : melanism in Cordylus polyzonus and terrestriality in Cordylus macropholis
Thesis (MSc)--Stellenbosch University, 2001.ENGLISH ABSTRACT: It has been suggested that rapid environmental change along the Western Cape coastal lowland
has had a profound bearing on the evolution of cordylid populations in this region. To test a
hypothesis on the evolution of melanism in the cordylid lizard, Cordylus polyzonus, the genetic
relationship among melanistic, turquoise and brown morphotypes in this species was examined
with allozyme electrophoresis. No polymorphic loci were found. No evidence was found that
the melanistic population was genetically distinct from the other colour morphotypes. The
results suggest that the studied melanistic population, is not a relict of a previously bigger
melanistic population, but simply an ecotype within a larger gene pool.
In the second section, some aspects of the ecology of the terrestrial lizard, Cordy Ius
macropholis were investigated. Implications of a proposed hypothesis on habitat transition in
this species, due to sea-level events, are discussed. Three complementary methods were used to
investigate habitat selection in C. macropholis in a natural area of Strandveld Succulent Karoo
vegetation. First, the sighting frequency of lizards in distinct plant categories was compared to
the relative availability of the habitats. Except for one case, all .sightings of lizards were made in
Euphorbia caput-medusae plants, the least available habitat category. Second, the habitat
preference of C. macropholis in terms of shelter quality was examined. Given a choice of three
shelter-types, both adult and juvenile lizards gave preference to E. caput-medusae, followed by
rock crevices and plant debris. Prey availability in E. caput-medusae plants was also found to be
consistent with prey items in the stomachs of C. macropholis at two independent sampling times.
Results indicated that C. macropholis shows a distinct preference for the relatively scarce refuge,
E. caput-medusae.
Given the preference for such a scarce resource, one might expect C. macropholis to compete
for potential mates that aggregate in these plants. To test this assumption, sex ratio, social structure, male spatial patterns and male social behaviour during the mating season were studied.
Repetitive sampling of two populations revealed highly female-biased sex ratios. Sex ratio was
found to relate positively to population density, as is the case in many polygynie lizard species.
However, the composition of aggregations pointed to a monogamous mating structure for this
species. In individual plants, segregation among adult males, and between adult males and
juvenile males was significantly higher within the reproductive season than outside. Adult males
also maintained a uniform spatial distribution within the reproductive season. Moreover, staged
encounters indicated that adult males behaved aggressively among themselves and toward
juvenile males, during the mating season. The data suggest that adult C. macropholis males are
territorial and that less dominant males may be excluded from E. caput-medusae plants to
habitats where their chances of survival may be lower.
By implication, one might predict that grouping behaviour in C. macropholis is not well
manifested and that movement of individuals among plants is high. This assumption was
validated by analyzing the size and stability of groups, as well as movement patterns among
plants. The size of aggregations within E. caput-medusae plants ranged from one to 14
individuals. Grouping was a year-round phenomenon, but aggregations exhibited a low degree
of long-term social structure. Site fidelity was low, with females showing significantly higher
site fidelity than males. Movement of individuals in and out of a marked population was high.
Results suggested no differential movement patterns between the sexes. The data confirmed that
aggregation behaviour and high degree of movement in C. macropholis are the result of mutual
competition for a limited plant resource.AFRIKAANSE OPSOMMING: Daar is voorgestel dat snelle omgewingsveranderinge aan die Wes-Kaap se kuslaagland, 'n
noemenswaardige effek op die evolusie van gordelakkedis-populasies in die gebied gehad het.
In die eerste deel van die ondersoek, is die genetiese verwantskap tussen melanistiese, turkoois
en bruin kleurmorfotipes in Cordylus polyzonus met behulp van ensiem-elektroforese bepaal.
Die doel was om 'n hipotese vir die evolusie van melanisme in die spesie te toets. Geen
polimorfiese lokusse is gevind nie. Daar was geen genetiese verskille tussen die melanistiese
populasie wat bestudeer is, en die turkoois of bruin populasies nie. Dit suggereer dat die
melanistiese populasie nie 'n oorblyfsel is van 'n eens groter melanistiese populasie nie, maar dat
dit eerder 'n ekotipe is in 'n groter geenpoel.
In die tweede gedeelte van die ondersoek, word enkele aspekte aangaande die ekologie van
die terrestriƫle gordelakkedis, Cordylus macropholis, ondersoek. Die implikasies van 'n
voorgestelde habitatsoorgang in die spesie as gevolg van omgewingsveranderinge, word
bespreek.
Habitatseleksie deur C. macropholis, in 'n natuurlike area binne die Sukkulente Strandveld
Karoo-bioom, is ondersoek met behulp van drie metodes. Eerstens, is die frekwensie van
akkedisse soos waargeneem in onderskeie plant-tipes, vergelyk met die relatiewe beskikbaarheid
van die plant-tipes. Behalwe vir een geval, is alle akkedisse waargeneem in Euphorbia caputmedusae
plante, die skaarsste van alle plant-tipes in die omgewing. Tweedens, is habitat keuse
in terme van skuiling ondersoek. 'n Keuse van E. caput-medusae plante, sandsteenskeure en
plantmateriaal is aan C. macropholis gestel. Beide volwasse en jong akkedisse het 'n voorkeur
getoon vir E. caput-medusae plante, gevolg deur klipskeure en plantmateriaal. Derdens, is
bepaal dat prooibeskikbaarheid in E. caput-medusae plante ooreenstem met die maaginhoude an C. macropholis gedurende twee verskillende tye. Dit is dus getoon dat C. macropholis 'n
duidelike voorkeur het vir die relatiewe skaars skuiling, E. caput-meduae.
Weens hierdie spesifieke voorkeur, is dit te wagte dat kompetisie vir potensiƫle maats, wat
saamgroepeer in die plant, sterk mag wees. Om hierdie aanname te toets, is die
geslagsverhouding en sosiale sisteem van C. macropholis, asook die ruimtelike verspreiding van
mannetjies en hulle gedrag binne die teelseisoen, bestudeer. Herhaalde studies het 'n
geslagsverhouding sterk ten gunste van wyfies getoon. Die geslagsverhouding het positief
gekorreleer met populasie-digtheid, soos wat die geval is in baie poligame spesies.
Samestellings van groepe akkedisse, het egter 'n monogame sosiale struktuur gesuggereer.
Segregasie tussen volwasse mannetjies en tussen volwasse mannetjies en jong mannetjies binne
plante, was aansienlik hoƫr gedurende die teelseisoen as buite die teelseisoen. Volwasse
mannetjies het ook 'n uniforme ruimtelike verspreiding getoon gedurende die teelseisoen. 'n
Laboratorium-eksperiment het verder aangetoon dat volwasse mannetjies, gedurende die
teelseioen, nie net aggressief teenoor mekaar optree nie, maar ook teenoor onvolwasse
mannetjies. Data stel dus voor dat volwasse mannetjies territoriaal is. Minder dominante
mannetjies mag uitgesluit word van E. caput-medusae plante en verdryf word na areas waar
hulle kanse op oorlewing minder mag wees.
By implikasie, is dit te wagte dat groepgedrag in C. macropholis nie sterk gemanifesteer is nie
en dat beweging van individue tussen plante aansienlik is. Die aanname is geƫvalueer deur die
grootte en stabiliteit van groepe in plante te monitor. Groepgrootte in E. caput-medusae plante
het gewissel van een tot 14 individue. Groepgedrag is regdeur diejaar opgemerk, maar groepe
het min tekens van langtermyn sosiale strukture getoon. Getrouheid aan spesifieke plantlokasies
was laag, hoewel wyfies meer getrou was aan spesifieke plantlokasies as mannetjies. Beweging
van individue in en uit die gemerkte populasie was hoog, maar resultate het geen differensiƫle
bewegingspatrone vir die twee geslagte aangetoon nie. Die data bevestig dat groepgedrag en hoƫ
mate van beweging in C. macropholis, die resultaat is van kompetisie vir 'n skaars hulpbron
The effects of coastal lowland instability : melanism in Cordylus polyzonus and terrestriality in Cordylus macropholis
Thesis (MSc)--Stellenbosch University, 2001.ENGLISH ABSTRACT: It has been suggested that rapid environmental change along the Western Cape coastal lowland
has had a profound bearing on the evolution of cordylid populations in this region. To test a
hypothesis on the evolution of melanism in the cordylid lizard, Cordylus polyzonus, the genetic
relationship among melanistic, turquoise and brown morphotypes in this species was examined
with allozyme electrophoresis. No polymorphic loci were found. No evidence was found that
the melanistic population was genetically distinct from the other colour morphotypes. The
results suggest that the studied melanistic population, is not a relict of a previously bigger
melanistic population, but simply an ecotype within a larger gene pool.
In the second section, some aspects of the ecology of the terrestrial lizard, Cordy Ius
macropholis were investigated. Implications of a proposed hypothesis on habitat transition in
this species, due to sea-level events, are discussed. Three complementary methods were used to
investigate habitat selection in C. macropholis in a natural area of Strandveld Succulent Karoo
vegetation. First, the sighting frequency of lizards in distinct plant categories was compared to
the relative availability of the habitats. Except for one case, all .sightings of lizards were made in
Euphorbia caput-medusae plants, the least available habitat category. Second, the habitat
preference of C. macropholis in terms of shelter quality was examined. Given a choice of three
shelter-types, both adult and juvenile lizards gave preference to E. caput-medusae, followed by
rock crevices and plant debris. Prey availability in E. caput-medusae plants was also found to be
consistent with prey items in the stomachs of C. macropholis at two independent sampling times.
Results indicated that C. macropholis shows a distinct preference for the relatively scarce refuge,
E. caput-medusae.
Given the preference for such a scarce resource, one might expect C. macropholis to compete
for potential mates that aggregate in these plants. To test this assumption, sex ratio, social structure, male spatial patterns and male social behaviour during the mating season were studied.
Repetitive sampling of two populations revealed highly female-biased sex ratios. Sex ratio was
found to relate positively to population density, as is the case in many polygynie lizard species.
However, the composition of aggregations pointed to a monogamous mating structure for this
species. In individual plants, segregation among adult males, and between adult males and
juvenile males was significantly higher within the reproductive season than outside. Adult males
also maintained a uniform spatial distribution within the reproductive season. Moreover, staged
encounters indicated that adult males behaved aggressively among themselves and toward
juvenile males, during the mating season. The data suggest that adult C. macropholis males are
territorial and that less dominant males may be excluded from E. caput-medusae plants to
habitats where their chances of survival may be lower.
By implication, one might predict that grouping behaviour in C. macropholis is not well
manifested and that movement of individuals among plants is high. This assumption was
validated by analyzing the size and stability of groups, as well as movement patterns among
plants. The size of aggregations within E. caput-medusae plants ranged from one to 14
individuals. Grouping was a year-round phenomenon, but aggregations exhibited a low degree
of long-term social structure. Site fidelity was low, with females showing significantly higher
site fidelity than males. Movement of individuals in and out of a marked population was high.
Results suggested no differential movement patterns between the sexes. The data confirmed that
aggregation behaviour and high degree of movement in C. macropholis are the result of mutual
competition for a limited plant resource.AFRIKAANSE OPSOMMING: Daar is voorgestel dat snelle omgewingsveranderinge aan die Wes-Kaap se kuslaagland, 'n
noemenswaardige effek op die evolusie van gordelakkedis-populasies in die gebied gehad het.
In die eerste deel van die ondersoek, is die genetiese verwantskap tussen melanistiese, turkoois
en bruin kleurmorfotipes in Cordylus polyzonus met behulp van ensiem-elektroforese bepaal.
Die doel was om 'n hipotese vir die evolusie van melanisme in die spesie te toets. Geen
polimorfiese lokusse is gevind nie. Daar was geen genetiese verskille tussen die melanistiese
populasie wat bestudeer is, en die turkoois of bruin populasies nie. Dit suggereer dat die
melanistiese populasie nie 'n oorblyfsel is van 'n eens groter melanistiese populasie nie, maar dat
dit eerder 'n ekotipe is in 'n groter geenpoel.
In die tweede gedeelte van die ondersoek, word enkele aspekte aangaande die ekologie van
die terrestriƫle gordelakkedis, Cordylus macropholis, ondersoek. Die implikasies van 'n
voorgestelde habitatsoorgang in die spesie as gevolg van omgewingsveranderinge, word
bespreek.
Habitatseleksie deur C. macropholis, in 'n natuurlike area binne die Sukkulente Strandveld
Karoo-bioom, is ondersoek met behulp van drie metodes. Eerstens, is die frekwensie van
akkedisse soos waargeneem in onderskeie plant-tipes, vergelyk met die relatiewe beskikbaarheid
van die plant-tipes. Behalwe vir een geval, is alle akkedisse waargeneem in Euphorbia caputmedusae
plante, die skaarsste van alle plant-tipes in die omgewing. Tweedens, is habitat keuse
in terme van skuiling ondersoek. 'n Keuse van E. caput-medusae plante, sandsteenskeure en
plantmateriaal is aan C. macropholis gestel. Beide volwasse en jong akkedisse het 'n voorkeur
getoon vir E. caput-medusae plante, gevolg deur klipskeure en plantmateriaal. Derdens, is
bepaal dat prooibeskikbaarheid in E. caput-medusae plante ooreenstem met die maaginhoude an C. macropholis gedurende twee verskillende tye. Dit is dus getoon dat C. macropholis 'n
duidelike voorkeur het vir die relatiewe skaars skuiling, E. caput-meduae.
Weens hierdie spesifieke voorkeur, is dit te wagte dat kompetisie vir potensiƫle maats, wat
saamgroepeer in die plant, sterk mag wees. Om hierdie aanname te toets, is die
geslagsverhouding en sosiale sisteem van C. macropholis, asook die ruimtelike verspreiding van
mannetjies en hulle gedrag binne die teelseisoen, bestudeer. Herhaalde studies het 'n
geslagsverhouding sterk ten gunste van wyfies getoon. Die geslagsverhouding het positief
gekorreleer met populasie-digtheid, soos wat die geval is in baie poligame spesies.
Samestellings van groepe akkedisse, het egter 'n monogame sosiale struktuur gesuggereer.
Segregasie tussen volwasse mannetjies en tussen volwasse mannetjies en jong mannetjies binne
plante, was aansienlik hoƫr gedurende die teelseisoen as buite die teelseisoen. Volwasse
mannetjies het ook 'n uniforme ruimtelike verspreiding getoon gedurende die teelseisoen. 'n
Laboratorium-eksperiment het verder aangetoon dat volwasse mannetjies, gedurende die
teelseioen, nie net aggressief teenoor mekaar optree nie, maar ook teenoor onvolwasse
mannetjies. Data stel dus voor dat volwasse mannetjies territoriaal is. Minder dominante
mannetjies mag uitgesluit word van E. caput-medusae plante en verdryf word na areas waar
hulle kanse op oorlewing minder mag wees.
By implikasie, is dit te wagte dat groepgedrag in C. macropholis nie sterk gemanifesteer is nie
en dat beweging van individue tussen plante aansienlik is. Die aanname is geƫvalueer deur die
grootte en stabiliteit van groepe in plante te monitor. Groepgrootte in E. caput-medusae plante
het gewissel van een tot 14 individue. Groepgedrag is regdeur diejaar opgemerk, maar groepe
het min tekens van langtermyn sosiale strukture getoon. Getrouheid aan spesifieke plantlokasies
was laag, hoewel wyfies meer getrou was aan spesifieke plantlokasies as mannetjies. Beweging
van individue in en uit die gemerkte populasie was hoog, maar resultate het geen differensiƫle
bewegingspatrone vir die twee geslagte aangetoon nie. Die data bevestig dat groepgedrag en hoƫ
mate van beweging in C. macropholis, die resultaat is van kompetisie vir 'n skaars hulpbron
Viewshed and sense of place as conservation features: A case study and research agenda for South Africa's national parks
Sense of place (SoP) refers to the meanings and values that people attach to places. The concept can be used to frame how people engage or form a connection with the natural environment. At a sensory level, SoP is influenced by peopleās visual experiences, which in turn can be linked to the concept of viewsheds. Viewsheds can be transformed, either abruptly (e.g. by infrastructure development such as wind turbines) or more gradually (e.g. by non-native trees invading a landscape). In this study, we focus on the Garden Route National Park to explore the potential importance of viewsheds as a conservation feature, specifically in the context of non-native (especially invasive) tree species. Using mixed information sources, we explore the potential role of invasive trees on experiences of visitors to this protected area and speculate on how viewsheds may shape SoP associations and how such associations may inform protected area management. Our investigation shows that peopleās experiences regarding natural and modified viewsheds are varied and intricate. Both SoP and viewsheds have the potential to inform conservation action, and these concepts should form an integral part of objective hierarchies and management plans for national parks. However, while legislation and park management plans make provision for the use of these concepts, associated research in South Africa is virtually non-existent. We conclude by proposing a conceptual model and research agenda to promote the use of viewsheds and SoP in the management of national parks in South Africa.
Conservation implications: Viewshed and sense of place can be used as boundary concepts to (1) facilitate interdisciplinary research between social and natural scientists, (2) help understand the connectedness and feedbacks between people and nature and (3) promote communication between science, management and stakeholders regarding desired conditions of landscapes in and around parks