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A role for pollinator-mediated facilitation in community assembly?
176
Abstracts
and process which can be followed for submissions for changes are outlined. doi:10.1016/j.sajb.2015.03.033
Variation in pollen–ovule ratio of southern African Periplocoideae (Apocynaceae): Evolutionary implications J.C.L. De Jager, L. Joubert, H.J.T. Venter, A.M. Venter Department of Plant Sciences, University of the Free State, PO Box 339, Bloemfontein 9301, South Africa Southern African Periplocoideae (Apocynaceae) are represented by seven genera, namely Cryptolepis R.Br., Ectadium E.Mey., Mondia Skeels, Petopentia Bullock, Raphionacme Harv., Stomatostemma N.E.Br. and Tacazzea Decne. Pollen is usually found as individual grains but in certain cases it is found as larger packaged units, such as in the Periplocoideae where two forms of pollen aggregation occur simultaneously; pollen tetrads deposited on translators. Aggregated pollen has evolved at least 39 times in angiosperms and at least three times in the Apocynaceae. Aggregated pollen has been shown to cause increased pollen transfer efficiency (PTE) which is hypothesised to be correlated with low pollen–ovule ratio. Previous research has shown that pollen aggregation in the Apocynaceae developed in reaction to aridification during glacial periods, which resulted in a pronounced mate finding allee effect. This suggests that that all Periplocoideae taxa, which have the same degree of pollen aggregation, should have similar pollen–ovule ratios and correlated PTE. The pollen–ovule ratio of representatives of all seven southern African Periplocoideae genera was determined and mapped onto an existing Periplocoideae phylogeny. A large variation in pollen–ovule ratio is shown among the seven Periplocoideae genera and it is therefore postulated that significant differences in the PTE of the seven genera exist. A difference in functional floral morphology and habitat of the seven genera was investigated as possible causes of the variation in PTE. doi:10.1016/j.sajb.2015.03.034
A role for pollinator-mediated facilitation in community assembly? M.L. De Jager, A.G. Ellis, B.A. Anderson Department of Botany and Zoology, Stellenbosch University, Matieland 7602, South Africa Studies on community assembly in plants have long focussed on the importance of abiotic factors in determining which species co-occur. Biotic factors, such as pollinator availability and abundance, have in recent years also been investigated in this regard. While the absence of a required pollinator may lead to exclusion from a community, pollinator sharing with existing community members can facilitate the establishment of new species. Sharing pollinators, however, may also lead to interspecific pollen transfer (IPT) that can decrease reproductive output. Pollinator constancy offers a likely, but under-studied mechanism to alleviate this cost. The diverse geophyte genus Oxalis represents an ideal system to explore these factors. Oxalis species often co-flower in the same site and share bee pollinators. A previous study on Oxalis communities in the Greater Cape Floristic Region revealed that coflowering species are more similar in flower colour than expected by chance. This was an unexpected pattern as transitions between species are more likely when they are similar in colour, suggesting a high incidence of IPT that has been shown to be detrimental within Oxalis. The observed pattern of colour similarity may, however, be driven by
facilitation where recent, and thus rare, species in a community benefit from sharing pollinators with common species that have similar floral colours. We explored this hypothesis through the use of floral arrays and fluorescent powder to track pollen movement between species that are similar and dissimilar in floral colour. We also analysed seedset in multispecies plots differing in the relative abundance of our focal species, Oxalis purpurea. Preliminary results indicate that colour similarity to co-flowering congeners may lead to increased seedset when the focal species is rare. This suggests that the benefits of increased pollen receipt outweigh the negative effects of IPT in rare species with similar flower colour to the background community. doi:10.1016/j.sajb.2015.03.035
Strigolactone signalling in Physcomitrella patens: Is locus Pp1s148_40v6 a MAX2 homolog? R.M. De Villiers, J. Kossmann, P.N. Hills Institute for Plant Biotechnology, Department of Genetics, Faculty of AgriSciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa On the basis of sequence homology, AtMAX2, the F-Box component of strigolactone signalling in Arabidopsis thaliana, has a distinct homolog in the genome of the bryophyte Physcomitrella patens. However, targeted knock-out of this locus leads to a novel phenotype that is unlike that of the characterised strigolactone biosynthesis mutant, Ppccd8Δ. While the Ppccd8Δ mutant favours colony expansion in the form of enhanced protonemal growth compared to the wild-type, the Ppmax2Δ mutant does not produce any protonemal tissue under standard growth conditions. Furthermore, the density of leaves on the Ppmax2Δ mutant (number of leaves/length) is significantly lower than in either Ppccd8Δ or the wild type. Nuclear localisation of the PpMAX2 protein is consistent with the nuclear localisation of MAX2 in the higher plants. In Arabidopsis, MAX2 expression is known to be localised to the vasculature and developing tissues, however, GUS expression in P. patens was localised to mature leaf tissue when driven by 1.96 kb of promoter sequence upstream of the PpMAX2 coding region. Taken together, these findings would suggest that the biological roles of the MAX2 homologs may not be conserved between vascular and non-vascular plants. doi:10.1016/j.sajb.2015.03.036
Floristics of KwaZulu-Natal Sandstone Sourveld within the eThekwini Municipal Area C. Drurya, S. Ramdhania, S. Naidooa, C. Carbuttb, R. Boodhraja, P. Mbathaa a School of Life Sciences, University of KwaZulu-Natal, Westville Campus, Private Bag X54001, Durban 4000, South Africa b Ezemvelo KZN Wildlife, Head Office, Queen Elizabeth Park, PO Box 13053, Cascades 3202, South Africa KwaZulu-Natal Sandstone Sourveld (KZNSS) is an endangered vegetation type in South Africa. Approximately 68% of KZNSS is transformed and it is ranked sixth nationally in terms of overall vulnerability. Fragmented patches of KZNSS found within the eThekwini Municipal Area (EMA) represent a conservation priority and due to transformation have become difficult to classify floristically. Indian Ocean Coastal Grassland Belt (IOCGB) patches found within close proximity to KZNSS patches need to be differentiated from KZNSS. For this purpose, floristic surveys were initiated in eight remnant grassland
Abstracts
and process which can be followed for submissions for changes are outlined. doi:10.1016/j.sajb.2015.03.033
Variation in pollen–ovule ratio of southern African Periplocoideae (Apocynaceae): Evolutionary implications J.C.L. De Jager, L. Joubert, H.J.T. Venter, A.M. Venter Department of Plant Sciences, University of the Free State, PO Box 339, Bloemfontein 9301, South Africa Southern African Periplocoideae (Apocynaceae) are represented by seven genera, namely Cryptolepis R.Br., Ectadium E.Mey., Mondia Skeels, Petopentia Bullock, Raphionacme Harv., Stomatostemma N.E.Br. and Tacazzea Decne. Pollen is usually found as individual grains but in certain cases it is found as larger packaged units, such as in the Periplocoideae where two forms of pollen aggregation occur simultaneously; pollen tetrads deposited on translators. Aggregated pollen has evolved at least 39 times in angiosperms and at least three times in the Apocynaceae. Aggregated pollen has been shown to cause increased pollen transfer efficiency (PTE) which is hypothesised to be correlated with low pollen–ovule ratio. Previous research has shown that pollen aggregation in the Apocynaceae developed in reaction to aridification during glacial periods, which resulted in a pronounced mate finding allee effect. This suggests that that all Periplocoideae taxa, which have the same degree of pollen aggregation, should have similar pollen–ovule ratios and correlated PTE. The pollen–ovule ratio of representatives of all seven southern African Periplocoideae genera was determined and mapped onto an existing Periplocoideae phylogeny. A large variation in pollen–ovule ratio is shown among the seven Periplocoideae genera and it is therefore postulated that significant differences in the PTE of the seven genera exist. A difference in functional floral morphology and habitat of the seven genera was investigated as possible causes of the variation in PTE. doi:10.1016/j.sajb.2015.03.034
A role for pollinator-mediated facilitation in community assembly? M.L. De Jager, A.G. Ellis, B.A. Anderson Department of Botany and Zoology, Stellenbosch University, Matieland 7602, South Africa Studies on community assembly in plants have long focussed on the importance of abiotic factors in determining which species co-occur. Biotic factors, such as pollinator availability and abundance, have in recent years also been investigated in this regard. While the absence of a required pollinator may lead to exclusion from a community, pollinator sharing with existing community members can facilitate the establishment of new species. Sharing pollinators, however, may also lead to interspecific pollen transfer (IPT) that can decrease reproductive output. Pollinator constancy offers a likely, but under-studied mechanism to alleviate this cost. The diverse geophyte genus Oxalis represents an ideal system to explore these factors. Oxalis species often co-flower in the same site and share bee pollinators. A previous study on Oxalis communities in the Greater Cape Floristic Region revealed that coflowering species are more similar in flower colour than expected by chance. This was an unexpected pattern as transitions between species are more likely when they are similar in colour, suggesting a high incidence of IPT that has been shown to be detrimental within Oxalis. The observed pattern of colour similarity may, however, be driven by
facilitation where recent, and thus rare, species in a community benefit from sharing pollinators with common species that have similar floral colours. We explored this hypothesis through the use of floral arrays and fluorescent powder to track pollen movement between species that are similar and dissimilar in floral colour. We also analysed seedset in multispecies plots differing in the relative abundance of our focal species, Oxalis purpurea. Preliminary results indicate that colour similarity to co-flowering congeners may lead to increased seedset when the focal species is rare. This suggests that the benefits of increased pollen receipt outweigh the negative effects of IPT in rare species with similar flower colour to the background community. doi:10.1016/j.sajb.2015.03.035
Strigolactone signalling in Physcomitrella patens: Is locus Pp1s148_40v6 a MAX2 homolog? R.M. De Villiers, J. Kossmann, P.N. Hills Institute for Plant Biotechnology, Department of Genetics, Faculty of AgriSciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa On the basis of sequence homology, AtMAX2, the F-Box component of strigolactone signalling in Arabidopsis thaliana, has a distinct homolog in the genome of the bryophyte Physcomitrella patens. However, targeted knock-out of this locus leads to a novel phenotype that is unlike that of the characterised strigolactone biosynthesis mutant, Ppccd8Δ. While the Ppccd8Δ mutant favours colony expansion in the form of enhanced protonemal growth compared to the wild-type, the Ppmax2Δ mutant does not produce any protonemal tissue under standard growth conditions. Furthermore, the density of leaves on the Ppmax2Δ mutant (number of leaves/length) is significantly lower than in either Ppccd8Δ or the wild type. Nuclear localisation of the PpMAX2 protein is consistent with the nuclear localisation of MAX2 in the higher plants. In Arabidopsis, MAX2 expression is known to be localised to the vasculature and developing tissues, however, GUS expression in P. patens was localised to mature leaf tissue when driven by 1.96 kb of promoter sequence upstream of the PpMAX2 coding region. Taken together, these findings would suggest that the biological roles of the MAX2 homologs may not be conserved between vascular and non-vascular plants. doi:10.1016/j.sajb.2015.03.036
Floristics of KwaZulu-Natal Sandstone Sourveld within the eThekwini Municipal Area C. Drurya, S. Ramdhania, S. Naidooa, C. Carbuttb, R. Boodhraja, P. Mbathaa a School of Life Sciences, University of KwaZulu-Natal, Westville Campus, Private Bag X54001, Durban 4000, South Africa b Ezemvelo KZN Wildlife, Head Office, Queen Elizabeth Park, PO Box 13053, Cascades 3202, South Africa KwaZulu-Natal Sandstone Sourveld (KZNSS) is an endangered vegetation type in South Africa. Approximately 68% of KZNSS is transformed and it is ranked sixth nationally in terms of overall vulnerability. Fragmented patches of KZNSS found within the eThekwini Municipal Area (EMA) represent a conservation priority and due to transformation have become difficult to classify floristically. Indian Ocean Coastal Grassland Belt (IOCGB) patches found within close proximity to KZNSS patches need to be differentiated from KZNSS. For this purpose, floristic surveys were initiated in eight remnant grassland