Question: Between Sidalcea and Backhousia, which genus can only be naturally found in Australia?

full_context: Document 1: Hymenosporum: Hymenosporum flavum, or native frangipani, is a rainforest tree which is native to Queensland and New South Wales in Australia and New Guinea. It is the sole species within the genus Hymenosporum, and is closely related to the widespread genus Pittosporum.
Document 2: Backhousia: Backhousia is a genus of thirteen currently known species of flowering plants in the family Myrtaceae. All the currently known species grow naturally only (endemic) in Australia in the rainforests and seasonally dry forests of Queensland, New South Wales and Western Australia.
Document 3: Buckinghamia: Buckinghamia is a genus of only two known species of trees, belonging to the plant family Proteaceae. They grow naturally only (endemic) in the rainforests of the wet tropics region of north eastern Queensland, Australia. The ivory curl flower, "B. celsissima", is the well known, popular and widely cultivated species in gardens and parks, in eastern and southern mainland Australia, and additionally as street trees north from about Brisbane. The second species, "B. ferruginiflora", was only recently described in 1988.
Document 4: Malva pusilla: Malva pusilla, also known as Malva rotundifolia (the latter of which is now officially rejected by botanists), the low mallow, small mallow, or the round-leaved mallow, is an annual and biennial herb species of the Mallow genus "Malva" in the family of Malvaceae. Malva is a genus that consists of about 30 species of plants. This genus consists of plants named mallows. Mallows grow in many regions, including temperate, subtropical, and tropical areas.
Document 5: Malacothamnus palmeri: Malacothamnus palmeri is a species of flowering plant in the mallow family known by the common names Palmer's bushmallow and Santa Lucia bushmallow. This flower is pink in color. It grows in openings in heavy chaparral and mixed evergreen forest. It requires adobe/shale to red clay type of soil to grow. The associated species are Quercus agrifolia, Adenostoma fasciculatum, Garrya elliptica, Rhamnus californica,Diplacus aurantiacus, Arctostaphylos luciana and Arbutus menziesii. A fast growing plant in most situations. The plant is fairly narrow (it will sucker to some degree) and will fit into a narrow flower bed.
Document 6: Melaleuca: Melaleuca is a genus of nearly 300 species of plants in the myrtle family, Myrtaceae, commonly known as paperbarks, honey-myrtles or tea-trees (although the last name is also applied to species of "Leptospermum"). They range in size from small shrubs that rarely grow to more than 1 m (3 ft) high, to trees up to 35 m (100 ft). Their flowers generally occur in groups, forming a “head” or “spike” resembling a brush used for cleaning bottles, containing up to 80 individual flowers. They are superficially like "Banksia" species, which also have their flowers in a spike, but the structures of individual flowers in the two genera are very different.
Document 7: Silene menziesii: Silene menziesii is a species of flowering plant in the pink family known by the common names Menzies' campion and Menzies' catchfly. It is native to western North America from Alaska through the western half of Canada to the southwestern United States. It can be found in many types of habitat and it is quite common in much of its range. It is variable in morphology and there are a number of varied subtaxa. In general, it is a perennial herb growing from a caudex, appearing matlike, decumbent, or erect, with stems a few centimeters to over half a meter long. It is usually hairy in texture, with upper parts bearing sticky glandular hairs. The leaves are lance-shaped, oppositely arranged in pairs, and a few centimeters in length, upper leaves usually smaller than lower. Flowers may occur in a cyme at the top of the stem, or in leaf axils, or both. Each is encapsulated in a hairy, veined calyx of fused sepals. The petals are white with two lobes at the tips. The plant is dioecious with male and female plants producing different flowers. The male and female flower types look the same externally; the stamens are reduced in female plants and the stigmas are reduced in the male.
Document 8: Physocarpus malvaceus: Physocarpus malvaceus is a species of flowering plant in the rose family known by the common name mallow ninebark. It is native to western North America, where its distribution extends from British Columbia to Nevada to Wyoming.
Document 9: Sidalcea: Sidalcea is a genus (approx. 25 species) of the botanical family Malvaceae. It contains several species of flower known generally as checkerblooms or checkermallows, or prairie mallows in the United Kingdom. They can be annuals or perennials, some rhizomatous. They are native to West and Central North America.
Document 10: Eucalyptus: Eucalyptus L'Héritier 1789 is a diverse genus of flowering trees and shrubs (including a distinct group with a multiple-stem mallee growth habit) in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia, and include "Eucalyptus regnans", the tallest known flowering plant on Earth. There are more than 700 species of eucalyptus and most are native to Australia; a very small number are found in adjacent areas of New Guinea and Indonesia. One species, "Eucalyptus deglupta," ranges as far north as the Philippines. Of the 15 species found outside Australia, just nine are exclusively non-Australian. Species of eucalyptus are cultivated widely in the tropical and temperate world, including the Americas, Europe, Africa, the Mediterranean Basin, the Middle East, China, and the Indian subcontinent. However, the range over which many eucalypts can be planted in the temperate zone is constrained by their limited cold tolerance. Australia is covered by 92000000 ha of eucalypt forest, comprising three quarters of the area covered by native forest.
Document 11: Boronia: Boronia is a genus of about 160 species of flowering plants in the citrus family Rutaceae, most are endemic in Australia with a few species in New Caledonia, which were previously placed in the genus "Boronella". They occur in all Australian states but the genus is under review and a number of species are yet to be described or the description published. Boronias are similar to familiar plants in the genera "Zieria", "Eriostemon" and "Correa" but can be distinguished from them by the number of petals or stamens. Some species have a distinctive fragrance and are popular garden plants.
Document 12: Malvaceae: Malvaceae, or the mallows, is a family of flowering plants estimated to contain 244 genera with 4225 known species. Well-known members of this family include okra, cotton, cacao and durian. The largest genera in terms of number of species include "Hibiscus" (300 species), "Sterculia" (250 species), "Dombeya" (250 species), "Pavonia" (200 species) and "Sida" (200 species).
Document 13: Sphaeralcea: Sphaeralcea is a genus of flowering plants in the mallow family (Malvaceae). There are about 40-60 species, including annuals, perennials, and shrubs. Most originate in the drier regions of North America, with some known from South America. They are commonly known as globemallows, globe mallows, or falsemallows. The name of the genus is derived from the Greek words σφαῖρα ("sphaira"), meaning "sphere," and αλκεα ("alkea"), meaning "mallow."
Document 14: Backhousia citriodora: Backhousia citriodora (common names lemon myrtle, lemon scented myrtle, lemon scented ironwood) is a flowering plant in the family Myrtaceae, genus "Backhousia". It is endemic to subtropical rainforests of central and south-eastern Queensland, Australia, with a natural distribution from Mackay to Brisbane. Other common names are sweet verbena tree, sweet verbena myrtle, lemon scented verbena, and lemon scented backhousia.
Document 15: Callirhoe (plant): Callirhoe is a genus of flowering plants in the mallow family, Malvaceae. Its nine species are commonly known as poppy mallows and all are native to the prairies and grasslands of North America. Of the nine, some are annuals while others are perennial plants.
ground_truth: Backhousia