Biogeography of cyclamen: an application of phyloclimatic modelling

© The Systematics Association 2011. Cyclamen is a genus of popular garden plant, protected by Convention on International Trade in Endangered Species (CITES) legislation. Many of its species are morphologically and phenologically adapted to the seasonal climate of the Mediterranean region. Most species occur in geographic isolation and will readily hybridise with their sister species when brought together. We investigate the biogeography of Cyclamen and assess the impact of palaeogeography and palaeoclimate change on the distribution of the genus. We use techniques of phyloclimatic modelling (combining ecological niche modelling and phylogenetic character optimisation) to investigate the heritability of climatic preference and to reconstruct ancestral niches. Conventional and phyloclimatic approaches to biogeography are compared to provide an insight into the historic distribution of Cyclamen species and the potential impact of climate change on their future distribution. The predicted climate changes over the next century could see a northward shift of many species’ climatic niches to places outside their current ranges. However, such distribution changes are unlikely to occur through natural antbased dispersal, so conservation measures are likely to be required

Plants at risk from climate change

The popular garden flower Cyclamen grows natively in the Mediterranean. Climate change could make the region unsuitable for 18/21 species in 50 years time. Ant-dispersed Cyclamen can’t hope to migrate to suitable new areas without assistance.

Background: The impact of global climate change on plant distribution, speciation and extinction is of current concern. Examining species climatic preferences via bioclimatic niche modelling is a key tool to study this impact. There is an established link between bioclimatic niche models and phylogenetic diversification. A next step is to examine future distribution predictions from a phylogenetic perspective. We present such a study using Cyclamen (Myrsinaceae), a group which demonstrates morphological and phenological adaptations to its seasonal Mediterranean-type climate. How will the predicted climate change affect future distribution of this popular genus of garden plants? 
Results: We demonstrate phylogenetic structure for some climatic characteristics, and show that most Cyclamen have distinct climatic niches, with the exception of several wide-ranging, geographically expansive, species. We reconstruct climate preferences for hypothetical ancestral Cyclamen. The ancestral Cyclamen lineage has a preference for the seasonal Mediterranean climate characteristic of dry summers and wet winters. Future bioclimatic niches, based on BIOCLIM and Maxent models, are examined with reference to a future climate scenario for the 2050s. Over the next 50 years we predict a northward shift in the area of climatic suitability, with many areas of current distribution becoming climatically unsuitable. The area of climatic suitability for every Cyclamen species is predicted to decrease. For many species, there may be no areas with a suitable climate regardless of dispersal ability, these species re considered to be at high risk of extinction. This risk is examined from a phylogenetic
perspective.
Conclusion: Examining bioclimatic niches from a phylogenetic perspective permits novel interpretations of these models. In particular, reconstruction of ancestral niches can provide testable hypothesis about the historical development of lineages. In the future we can expect a northwards shift in climatic suitability for the genus Cyclamen. If this proves to be the case then dispersal is the best chance of survival, which seems highly unlikely for ant-dispersed Cyclamen. Human-assisted establishment of Cyclamen species well outside their native ranges offers hope and could provide the only means of dispersal to potentially suitable future environments. Even without human intervention the phylogenetic perspective demonstrates that major lineages could survive climate change even if many species are lost

Automated pre-processing strategies for species occurrence data used in biodiversity modelling

To construct Biodiversity richness maps from Environmental Niche Models (ENMs) of thousands of species is time consuming. A separate species occurrence data pre-processing phase enables the experimenter to control test AUC score variance due to species dataset size. Besides, removing duplicate occurrences and points with missing environmental data, we discuss the need for coordinate precision, wide dispersion, temporal and synonymity filters. After species data filtering, the final task of a pre-processing phase should be the automatic generation of species occurrence datasets which can then be directly ’plugged-in’ to the ENM. A software application capable of carrying out all these tasks will be a valuable time-saver particularly for large scale biodiversity studies

Cyclamen libanoticum, a species that knows its identity!

The species limits and infraspecific DNA sequence diversity of Cyclamen libanoticum was examined. Analysis of the chloroplast DNA from six regions shows that, in C. libanoticum, only one base-pair difference is found among samples within the analysed 7066 base-pairs. This one base-pair difference (9 ‘A’s vs 10 ‘A’s) was found in the samples collected from a single site and could represent a very minor change in DNA sequence or even show the limits or accuracy of the sequencing system used. C. libanoticum is highly distinct from other congeners in DNA sequence

The Cyclamen graecum group, how many species?

Cyclamen graecum is a well-defined evolutionary unit that separated from other Cyclamen species about 10 million years ago (Yesson & Culham 2006; Yesson, Toomey & Culham, 2009). It is genetically isolated and there are no records of it hybridizing naturally with other species. However, over that time it has begun to form separate populations that themselves might later become species. The split between C. graecum subsp. graecum and C. graecum subsp. anatolicum, at 2.9-3.4mya, is older than the average speciation age of 2.3my for the genus Cyclamen (Yesson, Toomey & Culham, 2009), so it would be entirely consistent to treat C. graecum subsp. anatolicum as a species rather than a subspecies. Hildebrand’s name Cyclamen maritimum (Hildebrand, 1908, p291) is the earliest name available at species level. Therefore we propose that the the C. graecum group now comprises two species, one with two subspecies (Table 3). This would be consistent with species concepts elsewhere in the genus Cyclamen and properly reflect the genetic and geographic isolation of this element of the group

Mitochondrial and chloroplast DNA-based phylogeny of Pelargonium (Geraniaceae)

Overall phylogenetic relationships within the genus Pelargonium (Geraniaceae) were inferred based on DNA sequences from mitochondrial(mt)-encoded nad1 b/c exons and from chloroplast(cp)-encoded trnL (UAA) 5' exon-trnF (GAA) exon regions using two species of Geranium and Sarcocaulon vanderetiae as outgroups. The group II intron between nad1 exons b and c was found to be absent from the Pelargonium, Geranium, and Sarcocaulon sequences presented here as well as from Erodium, which is the first recorded loss of this intron in angiosperms. Separate phylogenetic analyses of the mtDNA and cpDNA data sets produced largely congruent topologies, indicating linkage between mitochondrial and chloroplast genome inheritance. Simultaneous analysis of the combined data sets yielded a well-resolved topology with high clade support exhibiting a basic split into small and large chromosome species, the first group containing two lineages and the latter three. One large chromosome lineage (x = 11) comprises species from sections Myrrhidium and Chorisma and is sister to a lineage comprising P. mutans (x = 11) and species from section Jenkinsonia (x = 9). Sister to these two lineages is a lineage comprising species from sections Ciconium (x = 9) and Subsucculentia (x = 10). Cladistic evaluation of this pattern suggests that x = 11 is the ancestral basic chromosome number for the genus

Phylogenetic study of Plectranthus, Coleus and allies (Lamiaceae): taxonomy, distribution and medicinal use

Lamiaceae subtribe Plectranthinae, a palaeotropical group of just over 450 species with mainly zygomorphic flowers and stamens that are contiguous at the point of insertion at the base of the lower corolla lip, include the medicinally and horticulturally important genus Plectranthus. Plectranthus currently includes the formerly recognized Coleus and Solenostemon. A phylogenetic analysis of the group is presented based on rps16, trnL-F and trnS-G regions of the plastid genome. Plectranthus as currently recognized is paraphyletic; a clade containing the type of Coleus and including Solenostemon, Pycnostachys and Anisochilus is sister to the rest of the group. Three endemic and monotypic Madagascan genera, Dauphinea, Madlabium, Perrierastrum and the Madagascan Capitanopsis belong to a single clade and are recognized under Capitanopsis; the new combinations are made here. Plectranthus s.s. is sister to a clade comprising Thorncroftia and Tetradenia. Tetradenia, unlike any other members of Plectranthinae, has actinomorphic corollas and is usually dioecious. A group of other species previously recognized as Plectranthus form a clade separate from Plectranthus s.s. and is recognized as Equilabium gen. nov. Estimates of clade age suggest that the genera begin to diversify from the mid to late Miocene. Plectranthinae are found in dry woodlands, montane grasslands and evergreen forest margins. Shifts between habitats occur in most clades, although significantly fewer than if the changes were random. The distribution of the clades in the major habitats is examined. Migration in Plectranthinae was from Africa to Madagascar and Asia, and there is no evidence of migration back to Africa. The phylogenetic pattern of medicinal use in Plectranthinae is weak, and issues surrounding this are discussed

Propagation of lusala (Dioscorea hirtiflora), a wild yam, for in situ and ex situ conservation and potential domestication

Lusala (Dioscorea hirtiflora Benth. subsp. pedicellata Milne-Redh) is an important wild edible tuber foraged widely from natural forests in Southern Zambia, but at risk from overharvesting and deforestation. Its propagation was investigated in glasshouse studies to explore potential domestication and future in situ and ex situ genetic resources conservation. Almost all tubers planted with visible shoot buds produced vines, with no effect of tuber size on vine emergence or tuber yield. Few tubers without visible shoot buds at planting produced vines, but those that did not re-tuberized. The progeny provided good vine emergence and similar tuber yield, with vines from tubers produced by re-tuberization being more vigorous. Re-tuberization in the absence of vine emergence also occurred in other experiments. Minisetts cut from the proximal end of tubers provided better vine emergence (with more from 20-mm than 10-mm long sections) and greater tuber yield than mid- or distal-minisetts. Nodal stem cuttings rooted well, vined, and provided small tubers. This study shows that lusala can be propagated successfully from tubers, minisetts, nodal vine cuttings, or mini-tubers from nodal vine cuttings, for genetic resources conservation and/or domestication. Domestication is likely to be hampered by the long period required for vines to emerge and establish. More sustainable foraging, including replanting in natural forests, is recommended to balance consumption of lusala in the region and promote its long-term conservation

Gardening in a changing climate

Since the 2002 publication of the RHS report looking at the impact of climate change on gardening, Gardening in a Global Greenhouse, the global climate has undergone dramatic change, with 2016 proving to be the warmest year on record. Today, confidence in global climate models has increased and we now know that extreme weather events are the most likely conditions to be experienced by the UK. The impact of these events, such as flash flooding and periods of drought, is likely to be compounded by increased housing pressure, meaning that gardens will become more critical in providing services formerly delivered by the natural environment – services such as flood alleviation, carbon sequestration and the provision of habitats for wildlife – that will be lost to development