Islands have played a key role in our understanding of rapid evolution. A large body of literature has examined morphological changes in response to insularity and isolation, which has yielded useful generalizations about how animals can adapt to live in very small geographic areas. However, understanding the evolution of morphological variation in insular populations often requires detailed data sets on longitudinal patterns of growth and development, and such studies typically necessitate long-term mark-recapture on a large sample of individuals. Rattlesnakes provide a unique opportunity to address some of these difficulties because the addition of rattle segments to the rattle string occurs with regular periodicity and their size directly correlates with the body size of the snake at the time of the ecdysis cycle generating the segment. Here, we used a large database of rattle segment sizes recorded from island (Isla Coronado Sur, Baja California, Mexico) and mainland (Camp Pendleton, California, United States) populations of Western Rattlesnakes (Crotalus oreganus and C. o. caliginis) that separated approximately 10,000 years ago to compare body sizes at different ecdysis cycles, which allowed us to assess differences in growth rates and patterns of sexual size dimorphism. Our results show that rattlesnakes on Isla Coronado Sur appear to be born smaller and grow more slowly than their mainland counterparts, resulting in a \"dwarfed\" island population. However, despite significant differences in body size, both populations exhibited the same degree of sexual dimorphism. Our study demonstrates the potential to use rattle characteristics to recover detailed estimates of fundamental demographic parameters.

The loss of defence hypothesis posits that island colonizers experience a release from predation on the mainland and subsequently lose their defensive adaptations. However, while support for the hypothesis from direct defensive traits is abundant, far less is known about indirect defensive traits. Leaf domatia are cave-like structures produced on the underside of leaves that facilitate an indirect defensive interaction with predaceous and microbivorous mites. I tested the loss of defence hypothesis in six domatia-bearing taxa inhabiting New Zealand and its offshore islands. No support for the loss of defence hypothesis was found. Changes in domatia investment were instead associated with changes in leaf size-a trait that has been repeatedly observed to undergo rapid evolution on islands. Overall results suggest that not all types of defence are lost on islands.

The species Homo luzonensis has recently been described based on a set of dental and postcranial elements found at Callao Cave (Northern Luzon, Philippines) and dated to at least 50-67 ka. Seven postcanine maxillary teeth are attributed to this taxon, five of them belonging to the same individual (CCH6) and representing the holotype of H. luzonensis, whereas the isolated upper premolar CCH8 and the upper third molar CCH9 are paratypes of the species. The teeth are characterized by their small dimensions associated with primitive features, as also found in Homo floresiensis, another hominin having evolved in an insular environment of Southeast Asia. Postcranial bones of the hands and feet of H. luzonensis and H. floresiensis show Homo habilis-like or australopith-like features, whereas cranial and dental morphology are more consistent with the Asian Homo erectus morphology. Due to this mosaic morphology, the origin and phylogenetic relationships of both H. luzonensis and H. floresiensis are still debated. To test the hypotheses that H. luzonensis derives from H. erectus or from an earlier small-brained hominin, we analyzed the µCT scans of the teeth. We investigated both external and internal tooth structure using morphometric methods including: crown outline shape, tooth crown tissue proportions, enamel-dentine junction shape, and pulp morphology. Homo luzonensis external crown morphology aligns more with H. erectus than with H. habilis/H. rudolfensis. The internal structural organization of H. luzonensis teeth exhibits more affinities with that of H. erectus and H. floresiensis than with Neanderthals and modern humans. Our results suggest that both H. floresiensis and H. luzonensis likely evolved from some H. erectus groups that dispersed in the various islands of this region and became isolated until endemic speciation events occurred at least twice during the Pleistocene in insular environments.

Evolution of vertebrate endemics in oceanic islands follows a predictable pattern, known as the island rule, according to which gigantism arises in originally small-sized species and dwarfism in large ones. Species of extinct insular giant rodents are known from all over the world. In the Canary Islands, two examples of giant rats, †Canariomys bravoi and †Canariomys tamarani, endemic to Tenerife and Gran Canaria, respectively, disappeared soon after human settlement. The highly derived morphological features of these insular endemic rodents hamper the reconstruction of their evolutionary histories. We have retrieved partial nuclear and mitochondrial data from †C. bravoi and used this information to explore its evolutionary affinities. The resulting dated phylogeny confidently places †C. bravoi within the African grass rat clade (Arvicanthis niloticus). The estimated divergence time, 650 000 years ago (95% higher posterior densities: 373 000-944 000), points toward an island colonization during the Günz-Mindel interglacial stage. †Canariomys bravoi ancestors would have reached the island via passive rafting and then underwent a yearly increase of mean body mass calculated between 0.0015 g and 0.0023 g; this corresponds to fast evolutionary rates (in darwins (d), ranging from 7.09 d to 2.78 d) that are well above those observed for non-insular mammals.

We are delighted that Diniz-Filho et al. agree with the main premise of our paper, and we welcome their critique, as constructive debate will help foster a better understanding of size evolution on islands. Our perspective on each of their criticisms is discussed in greater detail below.

By accompanying human travels since prehistorical times, the house mouse dispersed widely throughout the world, and colonized many islands. The origin of the travellers determined the phylogenetic source of the insular mice, which encountered diverse ecological and environmental conditions on the various islands. Insular mice are thus an exceptional model to disentangle the relative role of phylogeny, ecology and climate in evolution. Molar shape is known to vary according to phylogeny and to respond to adaptation. Using for the first time a three-dimensional geometric morphometric approach, compared with a classical two-dimensional quantification, the relative effects of size variation, phylogeny, climate and ecology were investigated on molar shape diversity across a variety of islands. Phylogeny emerged as the factor of prime importance in shaping the molar. Changes in competition level, mostly driven by the presence or absence of the wood mouse on the different islands, appeared as the second most important effect. Climate and size differences accounted for slight shape variation. This evidences a balanced role of random differentiation related to history of colonization, and of adaptation possibly related to resource exploitation.

Several plant traits are known to evolve in predictable ways on islands. For example, herbaceous species often evolve to become woody and species frequently evolve larger leaves, regardless of growth form. However, our understanding of how seed sizes might evolve on islands lags far behind other plant traits. Here, we conduct the first test for macroevolutionary patterns of seed size on islands. We tested for differences in seed size between 40 island-mainland taxonomic pairings from four island groups surrounding New Zealand. Seed size data were collected in the field and then augmented by published seed descriptions to produce a more comprehensive dataset. Seed sizes of insular plants were consistently larger than mainland relatives, even after accounting for differences in growth form, dispersal mode and evolutionary history. Selection may favour seed size increases on islands to reduce dispersibility, as long-distance dispersal may result in propagule mortality at sea. Alternatively, larger seeds tend to generate larger seedlings, which are more likely to establish and outcompete neighbours. Our results indicate there is a general tendency for the evolution of large seeds on islands, but the mechanisms responsible for this evolutionary pathway have yet to be fully resolved.