Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

The Theory of Island Biogeography

We used 5704 14C, 10Be, and 3He ages that span the interval from 10,000 to 50,000 years ago (10 to 50 ka) to constrain the timing of the Last Glacial Maximum (LGM) in terms of global ice-sheet and mountain-glacier extent. Growth of the ice sheets to their maximum positions occurred between 33.0 and 26.5 ka in response to climate forcing from decreases in northern summer insolation, tropical Pacific sea surface temperatures, and atmospheric CO2. Nearly all ice sheets were at their LGM positions from 26.5 ka to 19 to 20 ka, corresponding to minima in these forcings. The onset of Northern Hemisphere deglaciation 19 to 20 ka was induced by an increase in northern summer insolation, providing the source for an abrupt rise in sea level. The onset of deglaciation of the West Antarctic Ice Sheet occurred between 14 and 15 ka, consistent with evidence that this was the primary source for an abrupt rise in sea level ~14.5 ka.

https://science.sciencemag.org/content/sci/325/5941/710.full.pdf

The Last Glacial Maximum.

The revolution that wasn't: a new interpretation of the origin of modern human behavior.

Insect heritable symbionts have proven to be ubiquitous, based on molecular screening of various insect lineages. Recently, molecular and experimental approaches have yielded an immensely richer understanding of their diverse biological roles, resulting in a burgeoning research literature. Increasingly, commonalities and intermediates are being discovered between categories of symbionts once considered distinct: obligate mutualists that provision nutrients, facultative mutualists that provide protection against enemies or stress, and symbionts such as Wolbachia that manipulate reproductive systems. Among the most farreaching impacts of widespread heritable symbiosis is that it may promote speciation by increasing reproductive and ecological isolation of host populations, and it effectively provides a means for transfer of genetic information among host lineages. In addition, insect symbionts provide some of the extremes of cellular genomes, including the smallest and the fastest evolving, raising new questions about the limits of evolution of life.

Genomics and Evolution of Heritable Bacterial Symbionts

Bemisia tabaci has long been considered a complex species. It rose to global prominence in the 1980s owing to the global invasion by the commonly named B biotype. Since then, the concomitant eruption of a group of plant viruses known as begomoviruses has created considerable management problems in many countries. However, an enduring set of questions remains: Is B. tabaci a complex species or a species complex, what are Bemisia biotypes, and how did all the genetic variability arise? This review considers these issues and concludes that there is now sufficient evidence to state that B. tabaci is not made up of biotypes and that the use of biotype in this context is erroneous and misleading. Instead, B. tabaci is a complex of 11 well-defined high-level groups containing at least 24 morphologically indistinguishable species.

Bemisia tabaci: A Statement of Species Status

Runoff and erosion processes after a forest fire in Mount Carmel, a Mediterranean area

The sweet potato whitefly, Bemisia tabaci, harbors Portiera aleyrodidarum, an obligatory symbiotic bacterium, as well as several secondary symbionts including Rickettsia, Hamiltonella, Wolbachia, Arsenophonus, Cardinium and Fritschea, the function of which is unknown. Bemisia tabaci is a species complex composed of numerous biotypes, which may differ from each other both genetically and biologically. Only the B and Q biotypes have been reported from Israel. Secondary symbiont infection frequencies of Israeli laboratory and field populations of B. tabaci from various host plants were determined by PCR, in order to test for correlation between bacterial composition to biotype and host plant. Hamiltonella was detected only in populations of the B biotype, while Wolbachia and Arsenophonus were found only in the Q biotype (33% and 87% infection, respectively). Rickettsia was abundant in both biotypes. Cardinium and Fritschea were not found in any of the populations. No differences in secondary symbionts were found among host plants within the B biotype; but within the Q biotype, all whiteflies collected from sage harboured both Rickettsia and Arsenophonus, an infection frequency which was significantly higher than those found in association with all other host plants. The association found between whitefly biotypes and secondary symbionts suggests a possible contribution of these bacteria to host characteristics such as insecticide resistance, host range, virus transmission and speciation.

/pdf/biotype-dependent-secondary-symbiont-communities-in-n4uhu03bkt.pdf

Biotype-dependent secondary symbiont communities in sympatric populations of Bemisia tabaci.

Bacteria in the genus Rickettsia, best known as vertebrate pathogens vectored by blood-feeding arthropods, can also be found in phytophagous insects. The presence of closely related bacterial symbionts in evolutionarily distant arthropod hosts presupposes a means of horizontal transmission, but no mechanism for this transmission has been described. Using a combination of experiments with live insects, molecular analyses and microscopy, we found that Rickettsia were transferred from an insect host (the whitefly Bemisia tabaci) to a plant, moved inside the phloem, and could be acquired by other whiteflies. In one experiment, Rickettsia was transferred from the whitefly host to leaves of cotton, basil and black nightshade, where the bacteria were restricted to the phloem cells of the plant. In another experiment, Rickettsia-free adult whiteflies, physically segregated but sharing a cotton leaf with Rickettsia-plus individuals, acquired the Rickettsia at a high rate. Plants can serve as a reservoir for horizontal transmission of Rickettsia, a mechanism which may explain the occurrence of phylogenetically similar symbionts among unrelated phytophagous insect species. This plant-mediated transmission route may also exist in other insect–symbiont systems and, since symbionts may play a critical role in the ecology and evolution of their hosts, serve as an immediate and powerful tool for accelerated evolution.

/pdf/horizontal-transmission-of-the-insect-symbiont-rickettsia-is-4ugixlstgu.pdf

Horizontal transmission of the insect symbiont Rickettsia is plant-mediated.

Whiteflies (Homoptera: Aleyrodidae) comprise tiny phloem-sucking insects. The sessile development of their immatures and their phloem-feeding habits (with minimal physical plant damage) often lead to plant-mediated interactions with other organisms. The main data come from the polyphagous pest species Bemisia tabaci (Gennadius) and Trialeurodes vaporariorum (Westwood), which are intricately associated with their host plants. Although these associations might not represent aleyrodids in general, we rely on them to highlight the fundamental role of host plants in numerous ecological interactions between whiteflies, other herbivores, and their natural enemies. Plant traits often affect the activity, preference, and performance of the whiteflies, as well as their entomopathogens, predators, and parasitoids. Leaf structure (primarily pubescence) and constitutive and induced chemical profiles (defensive and nutritional elements) are critically important determinants of whitefly fitness. Pest management-related and evolutionary biology studies could benefit from future research that will consider whiteflies in a multitrophic-level framework.

Plant-Mediated Interactions Between Whiteflies, Herbivores, and Natural Enemies

Whiteflies (Homoptera: Aleyrodidae) comprise tiny phloemsucking insects. The sessile development of their immatures and their phloem-feeding habits (with minimal physical plant damage) often lead to plant-mediated interactions with other organisms. The main data come from the polyphagous pest species Bemisia tabaci (Gennadius) and Trialeurodes vaporariorum (Westwood), which are intricately associated with their host plants. Although these associations might not represent aleyrodids in general, we rely on them to highlight the fundamental role of host plants in numerous ecological interactions between whiteflies, other herbivores, and their natural enemies. Plant traits often affect the activity, preference, and performance of the whiteflies, as well as their entomopathogens, predators, and parasitoids. Leaf structure (primarily pubescence) and constitutive and induced chemical profiles (defensive and nutritional elements) are critically important determinants of whitefly fitness. Pest management–related and evolutionary biology studies could benefit from future research that will consider whiteflies in a multitrophiclevel framework.

Moshe Inbar

Papers

Runoff and erosion processes after a forest fire in Mount Carmel, a Mediterranean area

Biotype-dependent secondary symbiont communities in sympatric populations of Bemisia tabaci.

Horizontal transmission of the insect symbiont Rickettsia is plant-mediated.

Plant-Mediated Interactions Between Whiteflies, Herbivores, and Natural Enemies

Plant-Mediated Interactions Between Whiteflies, Herbivores, and Natural