PRELIMINARY TAXONOMIC STUDY ON HOMESTEAD FLORA OF FOUR DISTRICTS OF BANGLADESH: MAGNOLIOPSIDA

Abstract This study has documented the contemporary taxonomic information on the species of the class Magnoliopsida (Dicotyledons) extant in the homestead areas of Dhaka, Gazipur, Manikganj and Tangail districts of Bangladesh. In these areas, the Dicotyledons are comprised of total 455 species under 302 genera belonging to 78 families. Fabaceae with 41 species is the largest family and Solanum and Lindernia are the largest genera. Total 238 species are herbs followed by 129 species of trees and 88 species of shrubs. Total 332 species are economically useful. The composition and distribution of the species of this plant group are remarkably variable in the homestead areas of the four districts. The current status of seven threatened species viz., Abroma augusta, Andrographis paniculata, Aniseia martinicensis, Mucuna bracteata, Pterocarpus santalinus, Rauvolfia serpentina and Tournefortia roxburghii, included in the Red Data Book of Bangladesh and extant in the study area, has been evaluated and described. This study has identified some threats to the homestead flora and formulated some recommendations for the conservation of threatened and declining native plant species of the study area. The data provided by this study will serve as an important baseline to track the trend of changes in the floristic composition and diversity and sustainable development of plant genetic resources in the homesteads of the study area.


Introduction
Dicotyledons are the most successful and dominant plant group (Heywood, 1993). They comprise about 62.5% of the total angiosperm species (ca. 400000) recorded from this planet so far (Leitch and Leitch, 2008). Dicots are the major biotic component of almost all ecosystems and essential for human being as the source of food, cloths, shelter, medicines, fodder and many other substances used in different puroses worldwide. Bangladesh is endowed with about 5,000 species of flowering plants, of which more than two third are Dicotyledonous (Khan, 1972(Khan, -1987. Dicot plants dominate the forests, village groves and woodlands of Bangladesh (Khan and Afza, 1968;Khan and Banu, 1969;Khan, 1972Khan, -1987. Homesteads are privately owned dwellings in the rural and semi-urban settings that typically consist of a living area, kitchen, backyard, front yard, and sometimes a pond and patio (Muhammed et al., 2011). A homestead forest, or "homegarden", is usually a complex mixture of deliberately planted vegetation and designed to produce natural products for the household uses or market sale. It is an operational unit, in which a number of crops are grown with livestock, poultry and fish production mainly for the purpose of the farmer's basic needs (Leuschner and Khaleque, 1987). Bangladesh has 15.4 million homesteads occupying 0.3 million hectares of land that are providing major requirement of food, fruit, vegetables, timber and fuel wood (Abedin and Quddus, 1990). Plants of the homesteads are receiving increasing attention from scientists, practitioners and policymakers because of their social, economic, ecological and environmental benefits (Alam, 2011).
*Author for correspondence, email: roy_kbd@yahoo.com size, distribution range, and regeneration in the area, collections, interviews with elderly local people, and consulting the relevent IUCN guidelines (IUCN Standards and Petitions Committee, 2019).

Results and Discussion
This study recorded total 455 species of Magnoliopsida (Dicotyledons) under 302 genera and 78 families from the the visited homestead areas of Dhaka, Gazipur, Manikganj and Tangail districts (Table 1). Twenty three of the families were represented by single species each, 39 families by 2-10 species and only 13 families by 11-20 species. The homesteads of four districts  were dominated by the herbs (238 species; 52.31%) followed by trees (129 species; 28.35%) and shrubs (88 species; 19.34%). Among these species, 47 were climbers, six vines and four parasites.
These data indicate that the homestead areas of central region of Bangladesh still harbour a large number of Dicot species and they can serve as the hotspots of the flora and biodiversity of Bangladesh.
The taxonomic enumeration of the species of dicotyledons in the homestead areas of the four districts reported by this study seems lower than the record (605 species) of Tabassum (2015). This is due to the reason that Tabassum (2015) studied this plant group of whole Gazipur district consists of homestead and different non-homestead areas, the total land area of this district is much higher than that of the 1120 homesteads of four districts under this study, and in these homesteads, a good number of the species were overlapping and common. Most of other relevant studies conducted in plain land areas of this country mention the taxonomic account of Angiosperm species instead of dicot species. The enumeration of Angiosperm species by few of these studies (Kabir and Webb, 2009) are relatively higher, whereas, that of few other studies (Begum et al., 2013;Islam et al., 2013;Muhammed et al., 2011Muhammed et al., , 2013Rahman et al., 2009) are relatively lower than that of the dicot species by this study.
In the homesteads of the study area, Fabaceae with 41 species of 28 genera was recognized as the largest family that was followed by Euphorbiaceae with 34 species under 19 genera and Asteraceae with 26 species belonging to 22 genera. Solanum L. and Lindernia All. with eight species each was found as the largest genus in the study area, which was followed by Ficus L and Euphorbia L. with seven species each, Persicaria Mill. with six species and Albizia Durazz., Diospyros L. and Piper L. with five species each.
The composition and distribution of dicot species in the homestead areas of the four districts were remarkably variable. In the homesteads of Dhaka, Gazipur, Manikganj and Tangail districts, the occurance of total 283, 243, 285 and 223 species, respectively, was confirmed. Among these species, a total of 52, 35, 53 and 20 species were found to occur exclusively in the homesteads of native to Bangladesh. The occurrence of a good number of timber and fruit species in the homestead areas of the study area is supported by Bashar (1999 This study has provided field data on the current status of seven threatened species, included in the Red Data Book of Vascular Plants of Bangladesh (Khan et al., 2001;Ara et al., 2013), in the study area ( Table 2). The existing population size, number of localities, and estimated Extent of Occurrence (EOO) and Area of Occupancy (AOO) of these species were very narrow (Table 2). Moreover, all of these species were observed with poor regeneration and their localities were under the threats of continuous habitat destruction. Based on these facts, Abroma augusta (L.) L.f., Aniseia martinicensis (Jacq.) Choisy, Pterocarpus santalinus L.f. and Tournefortia roxburghii C.B. Clarke have been estimated as Critically Endangered (CE), Mucuna bracteata DC. ex Kurz and Rauvolfia serpentina (L.) Benth. ex Kurz as Endangered (E), and Andrographis paniculata (Burm.f.) Nees. as Vulnerable (V) in the homeatead areas of Dhaka, Gazipur, Manikganj and Tangail districts. This study provides basic taxonomic information on all species of dicotyledones including seven threatened species currently occurring in the homesteads area of central region of Bangladesh, which might serve as an important baseline to track the trend of changes in the floristic composition and biodiversity conservation in the homestead areas in course of time and different biogeographical processes. The data provided by this study might be useful in planning, management, conservation and sustainable development of homestead plant genetic resources in Bangladesh.
The increased human population and associated development activities in the last few decades has resulted directly in depletion of natural vegetation, which in turn increase the pressure on the homestead forest especially in the developing countries to meet various needs of the human beings (Alam et. al., 2005). This observation is found to be true in the homestead areas of the four districts studied. Additionally, habitat fragmentation and depletion, intrusion of exotic (e.g. Parthenium hysterophorus, Mikania cordata, Chromolaena odorata, Acacia auriculiformis and Eucalyptus camaldulensis) and parasitic species (e.g. Cuscuta reflexa, Dendrophthoe falcata, and Helixanthera cylindrica), vegetation clearing, unnecessary firing, unplanned agricultural extension, over exploitation of natural resources, lack of awareness in the local people including the homestead owners, and lack of proper management and protection systems homestead forests etc. are also the functional threats to the homestead flora, especially the threatened and declining native plant species, of the study area.
Therefore, appropriate planning, management strategies and measures, and awareness building programs should be effectively launched for the conservation of plant genetic resources in the homestead areas of this region. Performing studies on the natural regeneration, biogeography, and pollination, breeding and dispersal mechanisms of the threatened species threatened and declining native species of the region are very crucial for their sustainable conservation. Besides, effective attempts including the provision of incentives for involving the local people in conservation programs in the region is highly recommended.