Phytogeographical Significance Research Articles

Phytogeographical Significance of Endemic Genera (Angiosperms) in Peninsular India and Sri Lanka

The presence of eademic genera of restricted distribution occurring in Peninsular India and Sri Lanka is analysed in terms of its phytogeography. The genera are mainly of the palaeoendemic type. There are about 56 endemic genera in Peninsular India (Nayar, 1980) while in Sri Lanka there are only 20 genera. The presence of common genera (27 genera) with restricted distribution in Peninsular India and Sri Lanka is interesting from the phytogeographical angle.

Cordiaceae wood from the Miocene sediments of northeast India and its phytogeographical significance

Summary The order Boraginales of the Lamiids clade encompasses a diverse group of plants that currently has a global distribution. Its fossil record is scanty. Herein we report a fossil wood of Cordia L. of the family Cordiaceae from the Tipam Sandstone (late Miocene) sediments of Assam, northeast India. This finding not only throws light on the phytogeography and diversification of the Cordiaceae, but also provides valuable insights into the Neogene vegetation of the region.

Duabanga (Lythraceae) from the Oligocene of India and its climatic and phytogeographic significance

Understanding the evolutionary history of biodiversity hotspots has important implications for their future survival. India hosts four biodiversity hotspots: the Western Ghats of South India, the Andaman and Nicobar Islands, the Eastern Himalaya, and the Indo-Myanmar region. Northeast India (NEI) is an important region that hosts 43% of the total plant species occurring in India, of which ∼39% are endemic. This region also acts as a gateway for biotic exchange between India and southeast Asia. The area also receives exceptional rainfall during the pre-monsoon (March to May), in addition to the summer monsoon (June to September) season. In rainforests of NEI, forest-forming plant species make up a large proportion of the biodiversity. Understanding the evolutionary history of rainforests of NEI has implications for the conservation of biodiversity hotspots. Here we report the evergreen rainforest genus Duabanga Buch.-Ham. of the family Lythraceae from the late Oligocene sediments of Assam, NEI. Fossil records of this genus (from south and southeast Asia) suggest its Gondwanan origin, while its modern distribution is dominantly controlled by moisture availability.

The early Eocene flora of Horsefly, British Columbia, Canada and its phytogeographic significance

About forty species, including a bryophyte, ferns, conifers, Ginkgo, and over 35 angiosperms, are recognized based on compression-impression remains from the early Eocene of Horsefly, British Colombia, Canada. This flora is in the north central part of a chain of late early Eocene fossil assemblages known as floras of the “Okanagan Highlands” (= “Okanogan Highlands” in the US). These floras extend from north central British Columbia, Canada southeast to Republic, Washington, USA. The Horsefly flora shows similarities to other Eocene Okanagan Highlands floras, such as McAbee, Falkland, Thomas Ranch and Republic, but with some additional rare taxa. In the broader sense, the Horsefly flora can be compared with early and middle Eocene floras of eastern Asia and midcontinental North America, but shares fewer elements with Europe. Ginkgo, Metasequoia, Pinus, Palaeocarpinus, ulmaceous leaves and Deviacer are shared with northeastern China as well as western North American sites. Fagopsis, Macginitiea, Dipteronia, Florissantia, Sassafras and Lagokarpos also occur in other western North American Eocene floras and Koelreuteria and Jenkinsella with Eocene paleofloras of China. These comparisons demonstrate probable floristic exchange between northwestern North America and northeastern China via a Beringian route during the late early Eocene.

Plant fossils from the middle Siwalik of eastern Nepal and their climatic and phytogeographic significance

Plant fossils from the middle Siwalik of eastern Nepal and their climatic and phytogeographic significance

Tropidia thwaitesii Hook. f. (Orchidaceae: Tropidieae): A Little Known Orchid from Eastern Ghats, India

Tropidia thwaitesii Hook. f. is an overlooked Indo-Lankan orchid hitherto reported only from the Andaman Islands, Western Ghats of Tamil Nadu and Sri Lanka, and the present find from the tail end of Eastern Ghats is of phytogeographical significance. A detailed description, ecology, photographs and other relevant notes are provided for the better understanding and conservation of the taxa.

Annotated checklist of Cactaceae in the Catimbau National Park, Pernambuco, Brazil*

The cacti found at the Catimbau National Park in Pernambuco state, Brazil, are listed and the phytogeographical significance of the park is highlighted. Two new subspecies are described and the existence of three interspecific hybrids recorded. However, there exist conservation issues in this theoretically protected area.

Cordia diffusa K.C. Jacob, the Kovai Manjack (Boraginaceae): a highly threatened steno-endemic species from Coimbatore City, Tamil Nadu, India

Cordia diffusa K.C. Jacob, belonging to Boraginaceae, discovered in 1938 and named by K.C. Jacob in 1944, is a little-known and the only narrow endemic but neglected plant of Coimbatore City. The lectotype of the steno-endemic is determined and the current status, distribution, potential threats, bioprospecting potential, and suggestions for conservation of the species are discussed. The collection of steno-endemic plant during intensive exploration in its type locality nearly after 90 years is of phytogeographic and conservation significance. The endemic is proposed the category of Critically Endangered (CR) based on criterion D of IUCN (as per versions 3.1 & 13). C. diffusa can be protected by promoting awareness of the rarity of native species and mass propagation through vegetative means so as to introduce it in gardens, parks, and avenues, etc. at once in the city.

Cordia diffusa K.C. Jacob, the Kovai Manjack (Boraginaceae): a highly threatened steno-endemic species from Coimbatore City, Tamil Nadu, India

Cordia diffusa K.C. Jacob, belonging to Boraginaceae, discovered in 1938 and named by K.C. Jacob in 1944, is a little-known and the only narrow endemic but neglected plant of Coimbatore City. The lectotype of the steno-endemic is determined and the current status, distribution, potential threats, bioprospecting potential, and suggestions for conservation of the species are discussed. The collection of steno-endemic plant during intensive exploration in its type locality nearly after 90 years is of phytogeographic and conservation significance. The endemic is proposed the category of Critically Endangered (CR) based on criterion D of IUCN (as per versions 3.1 & 13). C. diffusa can be protected by promoting awareness of the rarity of native species and mass propagation through vegetative means so as to introduce it in gardens, parks, and avenues, etc. at once in the city.

Isoetes laurentiana, sp. nov. (Isoetaceae) endemic to freshwater tidal marshes in eastern Quebec, Canada

Morphological, phytogeographic, ecological, preliminary genetic, and C-value evidence indicates that populations of Isoetes confined to freshwater tidal marsh habitats along the St. Lawrence River in Quebec, Canada, represent an undescribed endemic species, proposed here as Isoetes laurentiana sp. nov. The combination of short velum coverage (ca. 10%) over a plain (unstreaked) sporangium, broad (ca. 1.0 mm) erect leaves, small megaspores (ca. 459 μm) with more densely convoluted-reticulate, almost echinate ornamentation, and its occurrence within an exceptional habitat, readily distinguish I. laurentiana from I. tuckermanii A.Braun with which it was formerly combined. Isoetes laurentiana is one of a series of endemic taxa of the floristically extraordinary St. Lawrence River estuary. Some populations of I. laurentiana are immense; in cultivation it demonstrates the capacity for prolific production of new individuals, which is presumably necessary to sustain such local abundance. Isoetes laurentiana is of national and global phytogeographic significance, but is not considered to represent a species at risk according to standards from the International Union for Conservation of Nature.

Diversity and ecology of the bryophytes in the cave environment: a study on the volcanic and karstic caves of Sicily

The results of a long investigation (20 years) on bryophyte diversity of 28 Sicilian caves are reported; the study regarded both karstic and volcanic caves, located at altitudes ranging from 15 to 2030 m a.s.l. The bryophyte diversity consists of a total of 136 taxa, 20 liverworts, 3 hornworts and 113 mosses. The ecological analysis was performed using the Ellenberg indicator values for moisture, light and soil reaction to the substrate. On the whole, mesophytic and meso-hygrophytic, sciophytic and photo-sciophytic species strongly prevail independently from the geological nature of the caves; the values of the soil reaction to the substrate well reflect the characteristics of the substrate. The phytogeographical analysis shows the prevalence of the Mediterranean species, followed by the temperate and southern-temperate species. It is remarkable the occurrence of boreo-arctic-montane species, which find refuge for their survival in some high-altitude caves. Some typical species well adapted to the cave environment are reported, including Amphidium mougeotii, Isopterygiopsis pulchella, Thamnobryum alopecurum and Rhynchostegiella tenella, showing a troglophilous character. The occurrence of species of phytogeographical significance, as well as of conservation interest, e.g. Ptychostomum cernuum, Tortula bolanderi, Rhabdoweisia fugax, Grimmia torquata, Brachytheciastrum collinum, very rare in Italy, is emphasized too.

Lagerstroemia L. wood from the Kimin Formation (Upper Siwalik) of Arunachal Pradesh and its Climatic and Phytogeographic Significance

ABSTRACT A fossil wood of Lagerstroemia L. from the Upper Siwalik sediments of Arunachal Pradesh is described. The genus is recorded for the first time from this state. The modern analog of the fossil species i.e. L. tomentosa C. Presl is not found in the fossil locality at present.. The most plausible reason for the disappearance of the species from the fossil locality is an increase in temperature seasonality caused by the upheaval of the Himalaya during the Pleistocene.

Fossil wood flora from the Siwalik Group of Arunachal Pradesh, India and its climatic and phytogeographic significance

The plant fossil records from the Siwalik Group of Arunachal Pradesh, India are far from satisfactory due to remoteness and dense vegetation of the area. We report seven fossil woods of which three belong to the Middle Siwalik (Subansiri Formation), while the rest are from the Upper Siwalik (Kimin Formation). The modern analogues of the fossils from the Middle Siwalik are Lophopetalum littorale (Celastraceae), Afzelia-Intsia and Sindora siamensis (Fabaceae) and from the Upper Siwalik are Miliusa velutina (Annonaceae), Calophyllum tomentosum and Kayea (Calophyllaceae) and Diospyros melanoxylon (Ebenaceae). The dominance of diffuse porosity in the fossil woods indicates a tropical climate with low seasonality (little variation) in temperature, while a high proportion of large vessels and simple perforation plates in the assemblage infer high precipitation during the deposition of the sediments. The aforesaid inference is in strong agreement with the previous quantitative reconstruction based on fossil leaves. Several modern analogues of the fossil taxa are now growing in low latitudes possibly due to an increase in seasonality (increased variation) in temperature caused by the rising Himalaya.

Thismia (Thismiaceae): the first record of the mycoheterotrophic genus to the Flora of India with a new species revealing the phytogeographical significance of Western Ghats

Thismia, a genus of mycoheterotrophic plants, is reported for the first time from mainland India, from Neryamangalam forests in Idukki district of Kerala, along with a new species, T. sahyadrica. Thismia sahyadrica, described and illustrated here, is unique within Thismia in having a mitre with a single opening; five perianth lobes are fused into a mitre-like structure, while the sixth one is free, forming a lateral single opening of the flower. Due to its unique morphological characteristics, the taxonomic placement of the new species remains obscure, although some root and flower characters suggest an affinity with species from the sections Glaziocharis, Sarcosiphon, Geomitra, and Scaphiophora. Ecological specificity and phytogeographical peculiarities of the new species are also discussed.

Palynofloral evolution on the northern margin of the Indian Plate, southern Xizang, China during the Cretaceous Period and its phytogeographic significance

During the Cretaceous Period, the Indian Plate separated from Gondwana and drifted northwards, eventually colliding with Eurasia at the end of the period or in the early Cenozoic. This led to major changes in the composition of the flora and fauna of the region. Palynomorph assemblages from Cretaceous deposits in Gamba County, southern Xizang (Tibet), China, are analyzed herein in an attempt to determine how the vegetation of the northern margin of the Indian Plate changed. The Gamba assemblages were initially similar in composition to those from Australia but by the Santonian Stage they were more similar to those of North Africa. Differences from the former are increasingly apparent through the Albian–Cenomanian transition. The rate of evolution of the Gamba flora was about the same as that of the Australian flora prior to the Albian, somewhat slower during this stage, but faster from the Cenomanian onwards, implying that this was, to a large extent, a result of the separation of the Indian Plate from Gondwana and its northward drift during the Cretaceous Period. During the Albian, the Australian block drifted eastwards whereas the Indian Plate remained relatively static. This resulted in few changes in the Gamba palynoflora but many in palynofloras from Australia. However, the northward movement of the Indian Plate in the Late Cretaceous led to pronounced changes, with numerous inceptions of genera and species in the Gamba succession. Of these, many have an African or equatorial distribution and none has connections with Australia, indicating that the climate at this time was similar to that of North Africa and that separation from Australia was complete. The arrival of the Indian Plate in equatorial regions allowed floral exchange between its northern part and North Africa during the Santonian.

First fossil evidence of Connaraceae R. Br. from Indian Cenozoic and its phytogeographical significance

Fossil leaflet impression described here as a new species Rourea miocaudata sp. nov., showing close resemblance with the modern leaflets of Rourea caudata Planch. (Connaraceae R. Br.), has been recorded from the lower part of the Siwalik sediments (Dafla Formation, middle–upper Miocene) exposed at the road-cutting section of Pinjoli area in West Kameng district, Arunachal Pradesh. The important morphological characters of the fossil are its narrow elliptic leaflet, cuneate base, long caudate apex, entire margin, eucamptodromous to brochidodromous secondary veins, presence of intersecondary veins, percurrent and reticulate tertiary veins and orthogonally reticulate quaternary veins. This is the first authentic record of the occurrence of leaflet comparable to R. caudata of Connaraceae from the Cenozoic sediments of India and abroad. At present R. caudata does not grow in India and is restricted only in southeast Asia especially in China and Myanmar. This taxon probably migrated to these southeast Asian regions after lower Siwalik sedimentation (middle–upper Miocene) due to climatic change caused by post-Miocene orogenic movement of the Himalaya. The recovery of this species and other earlier-described evergreen taxa from the same formation, suggests the existence of a tropical, warm and humid climatic conditions during the depositional period.

Phyllagathis Blume (Melastomataceae: Sonerileae), a new generic record for India with a new species

Phyllagathis indica is described as a new taxon from the Kuttikkanam Hills, Kerala section of the southern Western Ghats, India. The genus is new to the flora of India and hence has much phytogeographical significance. The diagnostic morphological characters, distribution, conservation status and images of the new species are presented in this paper.

Plant megaflora from the Siwalik (Upper Miocene) of Darjeeling District, West Bengal, India and its palaeoclimatic and phytogeographic significance

Qualitative and quantitative analysis of fossil assemblage so far collected from the Middle Siwalik sediments of Darjeeling District, West Bengal revealed the occurrence of 35 new taxa belonging to 18 angiospermous families. On the basis of present data as well as already known data from there, the reconstruction of vegetation scenarios of Himalayan foothills during Siwalik time has been done. We also discussed problems related to plant diversity, endemism, and migratory pathways of mainly phytogeographically important taxa. The analysis of present day distribution of all the recovered taxa from the region shows that they are mostly known to occur in Northeast India, Bangladesh, Myanmar and the Malayan region where the climatic conditions are favourable. About 1/3 taxa of total assemblage are found to grow presently in the Himalayan foothills of the eastern region and the remaining 2/3 taxa are locally extinct. This indicates that the climatic changes must have taken place after Mio–Pliocene. The dominance of evergreen elements in present fossil assemblage indicates the prevalence of tropical warm humid climate with plenty of rainfall during the deposition of sediments. Foliar physiognomic approach for reconstruction of palaeoclimate further suggests that the Oodlabari area in the Himalayan foothills of West Bengal enjoyed a tropical climate (with MAT 28.9º C and MAP 448 mm) during the Miocene Period. This is, however, contrary to the present day climate of the area with reduced precipitation. On the basis of the present fossil assemblage, the coexistence intervals of different climatic parameters, i.e. Mean Annual Temperature (MAT), Warmest Month Temperature (WMT), Coldest Month Temperature (CMT), and Mean Annual Precipitation (MAP) have been estimated as 22º C–26.5º C, 17.8º C–20º C, 25º C–30º C, and 2650–3200 mm, respectively. However, Leaf Margin Analysis (LMA) suggests the MAT value as 28.9º C for the area during Upper Miocene.

Fossil wood of Dipterocarpus from Nagri Formation (Middle Siwalik) of India: palaeoclimatic and phytogeographical significance

The paper reports the occurrence of fossil wood of Dipterocarpus (Dipterocarpaceae) from sandstone of Nagri Formation (Middle Siwalik), Saharanpur District, Uttar Pradesh, India. Present distribution of nearest living relatives (NLRs) of the fossil wood in the evergreen forests of Indo–Malaysian region indicates prevalence of tropical moist conditions in the Himalayan foot–hills in the Miocene in contrast to present day drier and cooler climate.

Occurrence of Gynocardia odorata Robert Brown (Achariaceae, formerly Flacourtiaceae) from the Plio-Pleistocene sediments of Arunachal Pradesh, northeast India and its palaeoclimatic and phytogeographic significance

This paper reports the occurrence of leaf impressions along with carbonised seeds, resembling those of Gynocardia odorata Robert Brown, in the late Pliocene to early Pleistocene sediments of the Kimin Formation exposed around Itanagar in Arunachal Pradesh. The recovery of this species and other earlier-described evergreen taxa from the same formation, suggests the existence of tropical, warm and humid climatic conditions during the depositional period. The seeds are here described as a new species Gynocardia arunachalensis Khan, Spicer TEV et Bera, sp. nov. So far, the report provides the first ever fossil record of Gynocardia seeds. We also characterise the nature of dispersal of this species in the past.