Species delimitation and biogeography of a southern hemisphere liverwort clade, Frullania subgenus Microfrullania (Frullaniaceae, Marchantiophyta)

Unveiling the diversification and dispersal of the Lewinskya firma complex (Orthotrichaceae, Bryophyta) across Africa and India

Intercontinental disjunctions are one of the most attractive and interesting biogeographical patterns. Bryophytes often exhibit such distributions, which is partly explained by their great ability to disperse over long distances. However, such intercontinental ranges are sometimes a distorted reality caused by the existence of unnoticed species. This study investigates whether the disjunction between East Africa and southern India of the moss Lewinskya firma reflects the genuine distribution of a single species or implies pseudo-cryptic species (whose morphological differentiation is subtle and have therefore been masked). An integrative taxonomic approach combining morphological and molecular methods (genotyping by sequencing, GBS) was used, based on a representation of samples specifically collected from all the major mountainous regions where this moss occurs. Two species, L. firma s. str. and L. afroindica sp. nov. are involved, whose ranges completely overlap in East Africa, although genetic distance and morphological differences in leaf apex shape, vaginula hairs shape and papillosity, spore ornamentation and peristome constitution and ornamentation allow distinguishing both. In addition, the range of L. afroindica extends into both southern Africa and southern India. The phylogenetic reconstruction obtained shows a certain degree of differentiation of the Indian populations, although they are yet morphologically indistinguishable from African populations. The results thus highlight both the existence of overlooked species and the complexity of bryophyte biogeography.

The roles of dispersal limitation, climatic niches and glacial history in endemism of the North American bryophyte flora

PREMISE

Bryophytes (mosses, liverworts, and hornworts) tend to have very large geographic ranges, which impedes progress toward understanding the drivers of diversification and extinction. This study aimed to investigate whether North American endemics differ geographically from more widespread species and whether differences in climatic niche or traits related to dispersal and establishment differ between endemics and more widespread species.

METHODS

All available herbarium records of bryophytes from North America north of Mexico (10⁶ collections) were used. Traits related to dispersal were obtained from the literature. Analyses tested whether range sizes and extents differed between endemics and nonendemics, and whether trait differences were associated with endemism. Climate data were used to determine whether differences in niche breadth are present between endemics and nonendemics, and whether suitable climate for endemics occurs outside North America.

RESULTS

Nonendemics have range sizes twice as large as endemics and they occur farther north and have greater longitudinal extents. However, they do not have the widest niche breadths and do not differ in spore size (with few exceptions) or sexual condition. Asexual propagules are more prevalent among nonendemics. Climatic models indicate that substantial areas of climate suitable for endemics exist outside of North America.

CONCLUSIONS

Distributions of endemics and nonendemics are consistent with an important role of glaciation in shaping the North American bryophyte flora. Endemics are not limited to the continent based on a lack of suitable climate elsewhere or by spore size or sexual condition.

On the diversity and distribution of the genus Frullania in Northern Holarctic

In Northern Holarctic, the liverwort genus Frullania includes 61 accepted species and at least ten undescribed new species making the genus the most diversified in that region. The presence of numerous endemics points to the role of the arising of new species, while the possible exchange between the continents through the Atlantic and Beringia land bridges resulted in species common for both North America and Eurasia.

An ancient tropical origin, dispersals via land bridges and Miocene diversification explain the subcosmopolitan disjunctions of the liverwort genus Lejeunea

Understanding the biogeographical and diversification processes explaining current diversity patterns of subcosmopolitan-distributed groups is challenging. We aimed at disentangling the historical biogeography of the subcosmopolitan liverwort genus Lejeunea with estimation of ancestral areas of origin and testing if sexual system and palaeotemperature variations can be factors of diversification. We assembled a dense taxon sampling for 120 species sampled throughout the geographical distribution of the genus. Lejeunea diverged from its sister group after the Paleocene-Eocene boundary (52.2 Ma, 95% credibility intervals 50.1-54.2 Ma), and the initial diversification of the crown group occurred in the early to middle Eocene (44.5 Ma, 95% credibility intervals 38.5-50.8 Ma). The DEC model indicated that (1) Lejeunea likely originated in an area composed of the Neotropics and the Nearctic, (2) dispersals through terrestrial land bridges in the late Oligocene and Miocene allowed Lejeunea to colonize the Old World, (3) the Boreotropical forest covering the northern regions until the late Eocene did not facilitate Lejeunea dispersals, and (4) a single long-distance dispersal event was inferred between the Neotropics and Africa. Biogeographical and diversification analyses show the Miocene was an important period when Lejeunea diversified globally. We found slight support for higher diversification rates of species with both male and female reproductive organs on the same individual (monoicy), and a moderate positive influence of palaeotemperatures on diversification. Our study shows that an ancient origin associated with a dispersal history facilitated by terrestrial land bridges and not long-distance dispersals are likely to explain the subcosmopolitan distribution of Lejeunea. By enhancing the diversification rates, monoicy likely favoured the colonisations of new areas, especially in the Miocene that was a key epoch shaping the worldwide distribution.

Climate-driven vicariance and long-distance dispersal explain the Rand Flora pattern in the liverwort Exormotheca pustulosa (Marchantiophyta)

The ‘Rand flora’ is a biogeographical disjunction which refers to plant lineages occurring at the margins of the African continent and neighbouring oceanic archipelagos. Here, we tested whether the phylogeographical pattern of Exormotheca pustulosa Mitt. was the result of vicariance induced by past climatic changes or the outcome of a series of recent long-distance dispersal events. Two chloroplast markers (rps4-trnF region and psbA-trnH spacer) and one nuclear marker (ITS2) were analysed. Phylogenetic and phylogeographical relationships were inferred as well as divergence time estimates and ancestral areas. Exormotheca possibly originated in Eastern Africa during the Late Oligocene/Early Miocene while Exormotheca putulosa diversified during the Late Miocene. Three main E. pustulosa groups were found: the northern Macaronesia/Western Mediterranean, the South Africa/Saint Helena and the Cape Verde groups. The major splits among these groups occurred during the Late Miocene/Pliocene; diversification was recent, dating back to the Pleistocene. Climate-driven vicariance and subsequent long-distance dispersal events may have shaped the current disjunct distribution of E. pustulosa that corresponds to the Rand Flora pattern. Colonization of Macaronesia seems to have occurred twice by two independent lineages. The evolutionary history of E. pustulosa populations of Cape Verde warrants further study.

Do mosses really exhibit so large distribution ranges? Insights from the integrative taxonomic study of the Lewinskya affinis complex (Orthotrichaceae, Bryopsida)

The strikingly lower number of bryophyte species, and in particular of endemic species, and their larger distribution ranges in comparison with angiosperms, have traditionally been interpreted in terms of their low diversification rates associated with a high long-distance dispersal capacity. This hypothesis is tested here with Lewinskya affinis (≡ Orthotrichum affine), a moss species widely spread across Europe, North and East Africa, southwestern Asia, and western North America. We tested competing taxonomic hypotheses derived from separate and combined analyses of multilocus sequence data, morphological characters, and geographical distributions. The best hypothesis, selected by a Bayes factor molecular delimitation analysis, established that L. affinis is a complex of no less than seven distinct species, including L. affinis s.str., L. fastigiata and L. leptocarpa, which were previously reduced into synonymy with L. affinis, and four new species. Discriminant analyses indicated that each of the seven species within L. affinis s.l. can be morphologically identified with a minimal error rate. None of these species exhibit a trans-oceanic range, suggesting that the broad distributions typically exhibited by moss species largely result from a taxonomic artefact. The presence of three sibling western North American species on the one hand, and four Old World sibling species on the other, suggests that there is a tendency for within-continent diversification rather than recurrent dispersal following speciation. The faster rate of diversification as compared to intercontinental migration reported here is in sharp contrast with earlier views of bryophyte species with wide ranges and low speciation rates.

The long journey of Orthotrichum shevockii (Orthotrichaceae, Bryopsida): From California to Macaronesia

Biogeography, systematics and taxonomy are complementary scientific disciplines. To understand a species’ origin, migration routes, distribution and evolutionary history, it is first necessary to establish its taxonomic boundaries. Here, we use an integrative approach that takes advantage of complementary disciplines to resolve an intriguing scientific question. Populations of an unknown moss found in the Canary Islands (Tenerife Island) resembled two different Californian endemic species: Orthotrichum shevockii and O. kellmanii. To determine whether this moss belongs to either of these species and, if so, to explain its presence on this distant oceanic island, we combined the evaluation of morphological qualitative characters, statistical morphometric analyses of quantitative traits, and molecular phylogenetic inferences. Our results suggest that the two Californian mosses are conspecific, and that the Canarian populations belong to this putative species, with only one taxon thus involved. Orthotrichum shevockii (the priority name) is therefore recognized as a morphologically variable species that exhibits a transcontinental disjunction between western North America and the Canary Islands. Within its distribution range, the area of occupancy is limited, a notable feature among bryophytes at the intraspecific level. To explain this disjunction, divergence time and ancestral area estimation analyses are carried out and further support the hypothesis of a long-distance dispersal event from California to Tenerife Island.

Using citizen science to bridge taxonomic discovery with education and outreach

PREMISE OF THE STUDY

Biological collections are uniquely poised to inform the stewardship of life on Earth in a time of cataclysmic biodiversity loss. Efforts to fully leverage collections are impeded by a lack of trained taxonomists and a lack of interest and engagement by the public. We provide a model of a crowd-sourced data collection project that produces quality taxonomic data sets and empowers citizen scientists through real contributions to science. Entitled MicroPlants, the project is a collaboration between taxonomists, citizen science experts, and teachers and students from universities and K-12.

METHODS

We developed an online tool that allows citizen scientists to measure photographs of specimens of a hyper-diverse group of liverworts from a biodiversity hotspot.

RESULTS

Using the MicroPlants online tool, citizen scientists are generating high-quality data, with preliminary analysis indicating non-expert data can be comparable to expert data.

DISCUSSION

More than 11,000 users from both the website and kiosk versions have contributed to the data set, which is demonstrably aiding taxonomists working toward establishing conservation priorities within this group. MicroPlants provides opportunities for public participation in authentic science research. The project's educational component helps move youth toward engaging in scientific thinking and has been adopted by several universities into curriculum for both biology and non-biology majors.