Taxonomic studies of the Genus Cotoneaster Ruppert ex Medikus of Pakistan and Azad Kashmir have been conducted, which presents the first detailed taxonomical work on the genus in Pakistan. No such studies were conducted on the genus before this in our country. Cotoneasteris a popular shrub or tree in the wild as well as a garden favourite. The genus was typified by the specimens from Europe. The materials for the studies were collected from the naturally occurring population and from herbarium specimens within the country. Specimens from the herbaria of the foreign countries were obtained on loan for studies. Characters such as habit, height of plants; shape and length of stipules; length and indumentum of petioles; arrangements, shape, size, texture, apices and indumentum on surfaces of leaves, the lengths of the largest leaves which is the most important character for the delimitation of species; number of flowers per cymes; nature of opening of flowers either all the same time or flowers open one after the other; shape, length and indumentum of hypanthia; erect or patent nature, colour, shape and apices of petals; number, size, colour, indumentum and apices of pomes; number and length of nutlets, have been found useful in the delimitation of species. The genus Cotoneaster has been classified into 2 sections, 4 sub-sections, 15 series and 63 species for Pakistan. Synonymy has been worked out, keys were formulated for the easy identification of the taxa and the species description were revised, all presented in the results section with figures, illustrations or pictures.
The species which have been studied taxonomiacally are as follows:-
1. C acuminatus Wall. ex Lindl., 2. C adpressus Boiss., 3. C affinis Wall. ex Lindl., 4. C afghanicus Klotz, 5. C aitchisonii Schneider, 6. C assamensis Klotz, 7. C bacillaris Wall. ex Lindl., 8. C brandisii Klotz, 9. C buxifolius Wall. ex Lindl., 10. C cashmiriensis Klotz, 11. C cavei Klotz, 12. C confusus Klotz, 13. C congestus Baker, 14. C duthieanus Klotz, 15. C ellipticus (Lindl.) Loudon (C lindley;, C insignus), 16. C falconeri Klotz, 17. C franchettii Boiss., 18. C frigidus Wall. Ex Lindl., 19. C gamblei Klotz, 20. C garhwalensis Klotz, 21. C gilgitensis Klotz, 22. C hissaricus Pojark., 23. C horizontalis Decaisne, 24. C humilis Dunn, 25. C ignotus Pojark., 26. C integerrimus Medik., 27. C integrifolius (Roxb.) Klotz, 28. C kaganensis Klotz, 29. C khasiensis Klotz, 30. C lacei Klotz, 31. C lambertii Klotz, 32. C marginatus (Loudon) Schlecht., 33. C meuselii Klotz, 34. C microphyllus Wall. ex Lindl., 35. C minutus Klotz, 36. C multiflorus Bunge, 37. C nitidus Jacq., 38. C nummularius Fisch. & Mey., 39. C nummularioides Pojark., 40. C obovatus Wall. ex Dunn, 41. C obtusus Wall. ex Lindl., 42. C osmastonii Klotz, 43. C pangiensis Klotz, 44. C pannosus Franchet, 45. C parkeri Klotz, 46. C parkinsonii Panigrahi and A. Kumar, 47. C prostratus Baker, 48. C pruinosus Klotz, 49. C racemiflorus (Desf.) C. Koch, 50. C rechingerii Klotz, 51. C roseus Edgew., 52. C rotundifolius Wall. ex Lindl., 53. C rubens W. W. Smith, 54. C sandakphuensis Klotz, 55. C sanguineus Vu, 56. C schlechtendalii Klotz, 57. C schubertii Klotz, 58. C stracheyi Klotz, 59. C symondsii Th. Moore, 60. C uniflorus Bunge, 61. C verruculosus Diels, 62. C wallichianus Klotz, & 63. C wattii Klotz. Out of the total 63 species, 44 are the new reports for Pakistan.
The habitats of the genus as observed in the field, are very characteristic Le. mostly arid, xeric rocks suffering from erosion but some were rocky slopes with established soil at protected places. Lizards, insects and birds were also observed in association with the species of Cotoneaster.
Being 95% apomictic it is concluded that the species with tree habit, longer leaves and even the species with larger leaf areas, acuminate or acute apices and petals patent are relatively more primitive than the species with prostrate habit, smaller leaves and leaf areas, emarginate apices and erect petals. The species with intermediate characters like erect or sub-erect habit, smaller leaves, with medium size, rounded, obtuse apices occupy the intermediate position. The data available on the anatomy, cytology and palynology has been correlated to confirm the classification, evolution and the status of the species.
The conclusion of the studies is that the genus contributes 63 species instead of 19 (Stewart, 1972) to the Family Rosaceae of Pakistan and 44 are new reports for Pakistan and Cotoneaster frigidus Wall.ex Lindl., is the most primitive in having tree habit 5-12 m tall, with patent petals, the largest leaf area of 6000 sqmm, with acute apices mostly, while C cavei Klotz is the most evolved in having prostrate habit, upto 0.8 m tall branches with erect petals, the largest leaf area of 60 sqmm and the leaves apices are emarginate. The species are the important component of the wild flora in the ecosystem as well as a garden favourite. The largest leaf area concept is an important additional tool for the classification and to know the evolution in the genus as proposed in this work.