Principios de Taxonomia

VIII Contents
6.12 Are Geographically Distant Populations of Stonechats (Saxicola torquata)
or Blackcaps (Sylvia atricapilla) Genetically Compatible? 146
6.13 Are Univoltine and Bivoltine Butterflies Able to Crossbreed? 148
6.14 Speciation Genes, Pre- and Postzygotic Barriers 149
6.15 Hybrid Incompatibility 151
6.16 Haldane s Rule and the Genes for Postzygotic Incompatibility 153
6.17 Sympatric and Allopatric Speciation 155
6.18 Sympatric Speciation in the Fruit fly Rhagoletis, in Cichlids
and in the Fire Salamander 159
6.19 Reproductive Incompatibility is Different than Phylogenetic
Distance 161
6.20 Phylogenetic Distance and Reproductive Incompatibility in Two Species
Pairs, Polar Bear (Ursus maritimus) and Brown Bear (U. arctos), in
Comparison to Grey Wolf (Canis lupus) and Coyote (C. latrans) 162
6.21 The Herring Gull (Larus argentatus) and the Greenish Warbler
(Phylloscopus trochiloides), a False and a True Model
for the Ring Species 163
6.22 Allopatrically Separated Populations are Always Different
Species 165
6.23 Species Hybrids as Exceptions without Evolutionary
Consequences 167
6.24 The Example of Some Duck Species: Extinction through
Hybridization 169
6.25 The Origin of Reproductive Isolation Through Reinforcement 171
6.26 Hybridogenic Speciation 173
6.27 Is the Italian Sparrow (Passer italiae) a Hybrid Species? 176
6.28 ‘‘Gene theft’’ between two Species of Galapagos Ground Finches 178
6.29 ‘‘Gene theft’’ between two Species of Green Frogs (Pelophylax ridibunda
and P. lessonae) 180
6.30 How many Genes Must Mutate for the Origin of New Species? 181
6.31 The Problem of Smooth Boundaries between two Gene-Flow
Communities 183
7 The Cohesion of Organisms Through Genealogical
Lineage (Cladistics) 187
7.1 Preliminary Remarks on Descent Connection 187
7.2 The Problem of Displaying the Phylogenetic Tree in the Case
of Biparental Reproduction 189
7.3 What are Species Boundaries in Cladistics? 191
7.4 How is a Cladistic Bifurcation Defined? Apomorphies and
Autapomorphies 194
7.5 Descent is not the Same Thing as Kinship: The Concepts
of Monophyly and Paraphyly 196
7.6 Why are Paraphyla used Despite their Inconsistency? 199
7.7 Monophyly and Paraphyly on Different Hierarchical Levels 202